Ukrainian President Petro Poroshenko gestures while speaking to the media during his news conference in Kiev, Ukraine, Sunday, Dec. 18, 2018. (AP Photo/Efrem Lukatsky)

Ukrainian President Petro Poroshenko speaking to the media during his news conference in Kiev, Ukraine, Sunday, Dec. 18, 2018. (AP Photo/Efrem Lukatsky)

Ukrainian President Petro Poroshenko speaking to the media during his news conference in Kiev, Ukraine, Sunday, Dec. 18, 2018. (AP Photo/Efrem Lukatsky)

Ukrainian President Petro Poroshenko keeps a rosary while speaking to the media during his news conference in Kiev, Ukraine, Sunday, Dec. 18, 2018. (AP Photo/Efrem Lukatsky)

Ukrainian President Petro Poroshenko speaks during a press conference in Kiev on December 16, 2018. - Tensions between Ukraine and Russia rose on November 25, when Russian forces seized three Ukranian navy vessels and their crew. Russia maintained an increased military presence on the Ukrainian border, having withdrawn "less than 10%" of its workforce since the peak of tension between the two countries, Ukrainian President Petro Poroshenko said on December 16, 2018. (Photo by Genya SAVILOV / AFP)

Ukrainian President Petro Poroshenko speaks during a press conference in Kiev on December 16, 2018. - Tensions between Ukraine and Russia rose on November 25, when Russian forces seized three Ukranian navy vessels and their crew. Russia maintained an increased military presence on the Ukrainian border, having withdrawn "less than 10%" of its workforce since the peak of tension between the two countries, Ukrainian President Petro Poroshenko said on December 16, 2018. (Photo by Genya SAVILOV / AFP)

Ukrainian President Petro Poroshenko speaks during a press conference in Kiev on December 16, 2018. - Tensions between Ukraine and Russia rose on November 25, when Russian forces seized three Ukranian navy vessels and their crew. Russia maintained an increased military presence on the Ukrainian border, having withdrawn "less than 10%" of its workforce since the peak of tension between the two countries, Ukrainian President Petro Poroshenko said on December 16, 2018. (Photo by Genya SAVILOV / AFP)

Ukrainian President Petro Poroshenko speaks during a press conference in Kiev on December 16, 2018. - Tensions between Ukraine and Russia rose on November 25, when Russian forces seized three Ukranian navy vessels and their crew. Russia maintained an increased military presence on the Ukrainian border, having withdrawn "less than 10%" of its workforce since the peak of tension between the two countries, Ukrainian President Petro Poroshenko said on December 16, 2018. (Photo by Genya SAVILOV / AFP)