Ukrainian soldiers move to position in an APC during military drills in base Honcharivske, Chernihiv region, Ukraine, Monday, Dec. 3, 2018. Ukraine???s president announced a partial call-up of reservists for training amid tensions with Russia, saying Monday that the country needs to beef up its defenses to counter the threat of a Russian invasion. (AP Photo/Efrem Lukatsky)

Ukrainian soldiers stand at a position during military drills in base Honcharivske, Chernihiv region, Ukraine, Monday, Dec. 3, 2018. Ukraine???s president announced a partial call-up of reservists for training amid tensions with Russia, saying Monday that the country needs to beef up its defenses to counter the threat of a Russian invasion. (AP Photo/Efrem Lukatsky)

Canadian Army Lieutenant General Jean-Marc Lanthier, left, addresses Ukrainian soldiers as Ukrainian President Petro Poroshenko, right, stands by during military drills in base Honcharivske, Chernihiv region, Ukraine, Monday, Dec. 3, 2018. Ukraine???s president announced a partial call-up of reservists for training amid tensions with Russia, saying Monday that the country needs to beef up its defenses to counter the threat of a Russian invasion. (AP Photo/Efrem Lukatsky)

Ukrainian soldiers move to position in an APC during military drills in base Honcharivske, Chernihiv region, Ukraine, Monday, Dec. 3, 2018. Ukraine???s president announced a partial call-up of reservists for training amid tensions with Russia, saying Monday that the country needs to beef up its defenses to counter the threat of a Russian invasion. (AP Photo/Efrem Lukatsky)

A tank moves to position during military drills in base Honcharivske, Chernihiv region, Ukraine, Monday, Dec. 3, 2018. Ukraine???s president announced a partial call-up of reservists for training amid tensions with Russia, saying Monday that the country needs to beef up its defenses to counter the threat of a Russian invasion. (AP Photo/Efrem Lukatsky)

Ukrainian President Petro Poroshenko, second left, addresses Ukrainian soldiers as Canadian Army Lieutenant General Jean-Marc Lanthier stands at center, and commander of U.S. Army in Europe Christopher Cavoli stands right, during military drills in base Honcharivske, Chernihiv region, Ukraine, Monday, Dec. 3, 2018. Ukraine???s president announced a partial call-up of reservists for training amid tensions with Russia, saying Monday that the country needs to beef up its defenses to counter the threat of a Russian invasion. (AP Photo/Efrem Lukatsky)

Ukrainian soldiers stand at a position during military drills in base Honcharivske, Chernihiv region, Ukraine, Monday, Dec. 3, 2018. President Petro Poroshenko says Russia has deployed a large number of troops along its border with Ukraine. He warns that Russia intends to push further inland into Ukraine following last week's naval clash between their forces in the Black Sea. Russia has already annexed the Black Sea peninsula of Crimea.(AP Photo/Efrem Lukatsky)

A security officer covers the back of Ukrainian President Petro Poroshenko during military drills in base Honcharivske, Chernihiv region, Ukraine, Monday, Dec. 3, 2018. President Petro Poroshenko says Russia has deployed a large number of troops along its border with Ukraine. He warns that Russia intends to push further inland into Ukraine following last week's naval clash between their forces in the Black Sea. Russia has already annexed the Black Sea peninsula of Crimea.(AP Photo/Efrem Lukatsky)

Ukrainian soldiers move to position in a APC during military drills in base Honcharivske, Chernihiv region, Ukraine, Monday, Dec. 3, 2018. President Petro Poroshenko says Russia has deployed a large number of troops along its border with Ukraine. He warns that Russia intends to push further inland into Ukraine following last week's naval clash between their forces in the Black Sea. Russia has already annexed the Black Sea peninsula of Crimea.(AP Photo/Efrem Lukatsky)

Ukrainian servicemen fire a gun as they take part in brigade tactical exercises with combat shooting near Goncharivske willage, Chernihiv region, not far from the border with Russia on December 3, 2018 - Tensions between Ukraine and Russia rose on November 25, when Russian forces seized three Ukranian navy vessels and their crew. Ukraine imposed martial law for 30 days in 10 regions that border Russia, the Black Sea and the Azov Sea on November 28. (Photo by Sergei SUPINSKY / AFP)

Ukrainian servicemen take part in brigade tactical exercises with combat shooting near Goncharivske village, Chernihiv region, not far from the border with Russia on December 3, 2018. - Tensions between Ukraine and Russia rose on November 25, when Russian forces seized three Ukranian navy vessels and their crew. Ukraine imposed martial law for 30 days in 10 regions that border Russia, the Black Sea and the Azov Sea on November 28. (Photo by Sergei SUPINSKY / AFP)

Ukrainian servicemen take part in brigade tactical exercises with combat shooting near Goncharivske village, Chernihiv region, not far from the border with Russia on December 3, 2018. - Tensions between Ukraine and Russia rose on November 25, when Russian forces seized three Ukranian navy vessels and their crew. Ukraine imposed martial law for 30 days in 10 regions that border Russia, the Black Sea and the Azov Sea on November 28. (Photo by Sergei SUPINSKY / AFP)

Ukrainian servicemen take part in brigade tactical exercises with combat shooting near Goncharivske village, Chernihiv region, not far from the border with Russia on December 3, 2018. - Tensions between Ukraine and Russia rose on November 25, when Russian forces seized three Ukranian navy vessels and their crew. Ukraine imposed martial law for 30 days in 10 regions that border Russia, the Black Sea and the Azov Sea on November 28. (Photo by Sergei SUPINSKY / AFP)

A Ukrainian serviceman takes part in brigade tactical exercises with combat shooting near Goncharivske village, Chernihiv region, not far from the border with Russia on December 3, 2018. - Tensions between Ukraine and Russia rose on November 25, when Russian forces seized three Ukranian navy vessels and their crew. Ukraine imposed martial law for 30 days in 10 regions that border Russia, the Black Sea and the Azov Sea on November 28. (Photo by Sergei SUPINSKY / AFP)

Ukrainian servicemen take part in brigade tactical exercises with combat shooting near Goncharivske willage, Chernihiv region, not far from the border with Russia on December 3, 2018. - Tensions between Ukraine and Russia rose on November 25, when Russian forces seized three Ukranian navy vessels and their crew. Ukraine imposed martial law for 30 days in 10 regions that border Russia, the Black Sea and the Azov Sea on November 28. (Photo by Sergei SUPINSKY / AFP)

Ukrainian servicemen take part in brigade tactical exercises with combat shooting near Goncharivske willage, Chernihiv region, not far from the border with Russia on December 3, 2018. - Tensions between Ukraine and Russia rose on November 25, when Russian forces seized three Ukranian navy vessels and their crew. Ukraine imposed martial law for 30 days in 10 regions that border Russia, the Black Sea and the Azov Sea on November 28. (Photo by Sergei SUPINSKY / AFP)

Ukrainian servicemen take part in brigade tactical exercises with combat shooting near Goncharivske willage, Chernihiv region, not far from the border with Russia on December 3, 2018. - Tensions between Ukraine and Russia rose on November 25, when Russian forces seized three Ukranian navy vessels and their crew. Ukraine imposed martial law for 30 days in 10 regions that border Russia, the Black Sea and the Azov Sea on November 28. (Photo by Sergei SUPINSKY / AFP)

Ukrainian servicemen take part in brigade tactical exercises with combat shooting near Goncharivske willage, Chernihiv region, not far from the border with Russia on December 3, 2018. - Tensions between Ukraine and Russia rose on November 25, when Russian forces seized three Ukranian navy vessels and their crew. Ukraine imposed martial law for 30 days in 10 regions that border Russia, the Black Sea and the Azov Sea on November 28. (Photo by Sergei SUPINSKY / AFP)

Ukrainian servicemen take part in brigade tactical exercises with combat shooting near Goncharivske willage, Chernihiv region, not far from the border with Russia on December 3, 2018. - Tensions between Ukraine and Russia rose on November 25, when Russian forces seized three Ukranian navy vessels and their crew. Ukraine imposed martial law for 30 days in 10 regions that border Russia, the Black Sea and the Azov Sea on November 28. (Photo by Sergei SUPINSKY / AFP)

Ukrainian President Petro Poroshenko speaks to the servicemen taking part in brigade tactical exercises with combat shooting near Goncharivske willage, Chernihiv region, not far from the border with Russia on December 3, 2018. - Tensions between Ukraine and Russia rose on November 25, when Russian forces seized three Ukranian navy vessels and their crew. Ukraine imposed martial law for 30 days in 10 regions that border Russia, the Black Sea and the Azov Sea on November 28. (Photo by Sergei SUPINSKY / AFP)

Ukrainian President Petro Poroshenko (C) greets the servicemen taking part in brigade tactical exercises with combat shooting near Goncharivske willage, Chernihiv region, not far from the border with Russia on December 3, 2018. - Tensions between Ukraine and Russia rose on November 25, when Russian forces seized three Ukranian navy vessels and their crew. Ukraine imposed martial law for 30 days in 10 regions that border Russia, the Black Sea and the Azov Sea on November 28. (Photo by Sergei SUPINSKY / AFP)

Ukrainian President Petro Poroshenko (C,L) speaks to the servicemen taking part in brigade tactical exercises with combat shooting near Goncharivske willage, Chernihiv region, not far from the border with Russia on December 3, 2018. - Tensions between Ukraine and Russia rose on November 25, when Russian forces seized three Ukranian navy vessels and their crew. Ukraine imposed martial law for 30 days in 10 regions that border Russia, the Black Sea and the Azov Sea on November 28. (Photo by Sergei SUPINSKY / AFP)

Ukrainian servicemen on armored personal carriers (APC) take part in brigade tactical exercises with combat shooting near Goncharivske willage, Chernihiv region, not far from the border with Russia on December 3, 2018. - Tensions between Ukraine and Russia rose on November 25, when Russian forces seized three Ukranian navy vessels and their crew. Ukraine imposed martial law for 30 days in 10 regions that border Russia, the Black Sea and the Azov Sea on November 28. (Photo by Sergei SUPINSKY / AFP)

Ukrainian servicemen on armored personal carriers (APC) take part in brigade tactical exercises with combat shooting near Goncharivske willage, Chernihiv region, not far from the border with Russia on December 3, 2018. - Tensions between Ukraine and Russia rose on November 25, when Russian forces seized three Ukranian navy vessels and their crew. Ukraine imposed martial law for 30 days in 10 regions that border Russia, the Black Sea and the Azov Sea on November 28. (Photo by Sergei SUPINSKY / AFP)

Ukrainian servicemen take part in brigade tactical exercises with combat shooting near Goncharivske willage, Chernihiv region, not far from the border with Russia on December 3, 2018. - Tensions between Ukraine and Russia rose on November 25, when Russian forces seized three Ukranian navy vessels and their crew. Ukraine imposed martial law for 30 days in 10 regions that border Russia, the Black Sea and the Azov Sea on November 28. (Photo by Sergei SUPINSKY / AFP)

A helicopter of Ukrainian President Petro Poroshenko flies over a serviceman prior brigade tactical exercises with combat shooting near Goncharivske village, Chernihiv region, not far from the border with Russia on December 3, 2018. - Tensions between Ukraine and Russia rose on November 25, when Russian forces seized three Ukranian navy vessels and their crew. Ukraine imposed martial law for 30 days in 10 regions that border Russia, the Black Sea and the Azov Sea on November 28. (Photo by Sergei SUPINSKY / AFP)

TOPSHOT - Ukrainian servicemen fire a gun as they take part in brigade tactical exercises with combat shooting near Goncharivske willage, Chernihiv region, not far from the border with Russia on December 3, 2018 - Tensions between Ukraine and Russia rose on November 25, when Russian forces seized three Ukranian navy vessels and their crew. Ukraine imposed martial law for 30 days in 10 regions that border Russia, the Black Sea and the Azov Sea on November 28. (Photo by Sergei SUPINSKY / AFP)

TOPSHOT - A helicopter of Ukrainian President Petro Poroshenko flies over a serviceman prior brigade tactical exercises with combat shooting near Goncharivske village, Chernihiv region, not far from the border with Russia on December 3, 2018. - Tensions between Ukraine and Russia rose on November 25, when Russian forces seized three Ukranian navy vessels and their crew. Ukraine imposed martial law for 30 days in 10 regions that border Russia, the Black Sea and the Azov Sea on November 28. (Photo by Sergei SUPINSKY / AFP)

TOPSHOT - Ukrainian servicemen take part in brigade tactical exercises with combat shooting near Goncharivske willage, Chernihiv region, not far from the border with Russia on December 3, 2018. - Tensions between Ukraine and Russia rose on November 25, when Russian forces seized three Ukranian navy vessels and their crew. Ukraine imposed martial law for 30 days in 10 regions that border Russia, the Black Sea and the Azov Sea on November 28. (Photo by Sergei SUPINSKY / AFP)

Ukrainian servicemen take part in brigade tactical exercises with combat shooting near Goncharivske village, Chernihiv region, not far from the border with Russia on December 3, 2018. - Tensions between Ukraine and Russia rose on November 25, when Russian forces seized three Ukranian navy vessels and their crew. Ukraine imposed martial law for 30 days in 10 regions that border Russia, the Black Sea and the Azov Sea on November 28. (Photo by Sergei SUPINSKY / AFP)

Ukrainian servicemen take part in brigade tactical exercises with combat shooting near Goncharivske village, Chernihiv region, not far from the border with Russia on December 3, 2018. - Tensions between Ukraine and Russia rose on November 25, when Russian forces seized three Ukranian navy vessels and their crew. Ukraine imposed martial law for 30 days in 10 regions that border Russia, the Black Sea and the Azov Sea on November 28. (Photo by Sergei SUPINSKY / AFP)