German Minister for Foreign Affairs Heiko Maas, left, and his Ukrainian counterpart Pavlo Klimkin shake hands during their meeting in Kiev, Ukraine, Friday, Jan. 18, 2019. (AP Photo/Efrem Lukatsky)

German Minister for Foreign Affairs Heiko Maas, left, and his Ukrainian counterpart Pavlo Klimkin shake hands during their meeting in Kiev, Ukraine, Friday, Jan. 18, 2019. (AP Photo/Efrem Lukatsky)

German Minister for Foreign Affairs Heiko Maas, left, and his Ukrainian counterpart Pavlo Klimkin shake hands during their meeting in Kiev, Ukraine, Friday, Jan. 18, 2019. (AP Photo/Efrem Lukatsky)

German Minister for Foreign Affairs Heiko Maas, left, and his Ukrainian counterpart Pavlo Klimkin at a joint press conference in Kiev, Ukraine, Friday, Jan. 18, 2019. (AP Photo/Efrem Lukatsky)

Ukrainian Minister for Foreign Affairs Pavlo Klimkin speaks at a joint press conference with German Minister for Foreign Affairs Heiko Maas in Kiev, Ukraine, Friday, Jan. 18, 2019. (AP Photo/Efrem Lukatsky)

German Minister for Foreign Affairs Heiko Maas attends a joint press conference with Ukrainian counterpart Pavlo Klimkin in Kiev, Ukraine, Friday, Jan. 18, 2019. (AP Photo/Efrem Lukatsky)

Ukrainian President Petro Poroshenko, left, and German Minister for Foreign Affairs Heiko Maas talk during their meting in Kiev, Ukraine, Friday, Jan. 18, 2019. (Mykola Lazarenko/Presidential Press Service Pool Photo via AP)

Ukraine's Minister of Foreign Affairs of Ukraine Pavlo Klimkin (R) welcomes his German counterpart Heiko Maas during their meeting prior in Kiev on January 18, 2019. (Photo by SERGEI SUPINSKY / AFP)

Ukraine's Minister of Foreign Affairs of Ukraine Pavlo Klimkin (R) welcomes his German counterpart Heiko Maas during their meeting prior in Kiev on January 18, 2019. (Photo by SERGEI SUPINSKY / AFP)

Ukraine's Minister of Foreign Affairs of Ukraine Pavlo Klimkin (R) welcomes his German counterpart Heiko Maas during their meeting prior in Kiev on January 18, 2019. (Photo by SERGEI SUPINSKY / AFP)

Ukraine's Minister of Foreign Affairs of Ukraine Pavlo Klimkin (R) listens as his German counterpart Heiko Maas during their press conference for the results of their talks in Kiev on January 18, 2019. (Photo by Sergei SUPINSKY / AFP)

Ukraine's Minister of Foreign Affairs of Ukraine Pavlo Klimkin (R) and his German counterpart Heiko Maas give a joint press conference following talks in Kiev on January 18, 2019. (Photo by Sergei SUPINSKY / AFP)

Ukraine's Minister of Foreign Affairs of Ukraine Pavlo Klimkin (R) listens as his German counterpart Heiko Maas during a joint press conference following talks in Kiev on January 18, 2019. (Photo by Sergei SUPINSKY / AFP)

Ukraine's Minister of Foreign Affairs of Ukraine Pavlo Klimkin (R) and his German counterpart Heiko Maas give a joint press conference following talks in Kiev on January 18, 2019. (Photo by Sergei SUPINSKY / AFP)

Ukraine's Minister of Foreign Affairs of Ukraine Pavlo Klimkin (R) and his German counterpart Heiko Maas give a joint press conference following talks in Kiev on January 18, 2019. (Photo by Sergei SUPINSKY / AFP)

Ukraine's Minister of Foreign Affairs Pavlo Klimkin (R) and his German counterpart Heiko Maas shake hands after their press-conference following their meeting in Kiev on January 18, 2019. (Photo by Sergei SUPINSKY / AFP)

Ukraine's Minister of Foreign Affairs Pavlo Klimkin (R) and his German counterpart Heiko Maas shake hands after their press-conference following their meeting in Kiev on January 18, 2019. (Photo by Sergei SUPINSKY / AFP)

This handout picture taken and released by the Ukrainian presidential press service on January 18, 2019 shows Ukrainian President Petro Poroshenko (L) shaking hands with German Foreign Affairs Minister Heiko Maas during their meeting in Kiev. (Photo by MYKOLA LAZARENKO / UKRAINIAN PRESIDENTIAL PRESS SERVICE / AFP) / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / UKRAINIAN PRESIDENTIAL PRESS SERVICE / MYKOLA LAZARENKO- NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS

This handout picture taken and released by the Ukrainian presidential press service on January 18, 2019 shows Ukrainian President Petro Poroshenko (L) speaking with German Foreign Affairs Minister Heiko Maas during their meeting in Kiev. (Photo by MYKOLA LAZARENKO / UKRAINIAN PRESIDENTIAL PRESS SERVICE / AFP) / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / UKRAINIAN PRESIDENTIAL PRESS SERVICE / MYKOLA LAZARENKO- NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS

18 January 2019, Ukraine, Kiew: Heiko Maas (SPD, l), Foreign Minister, is received by his Ukrainian counterpart Pawlo Klimkin at the Ukrainian Foreign Ministry. The main topics of the trip are the Ukraine crisis, the peace efforts in Syria and the dispute over the INF treaty banning nuclear medium-range missiles. Photo: Kay Nietfeld/dpa

18 January 2019, Ukraine, Kiew: Heiko Maas (SPD, l), Foreign Minister, is received by his Ukrainian counterpart Pawlo Klimkin at the Ukrainian Foreign Ministry. The main topics of the trip are the Ukraine crisis, the peace efforts in Syria and the dispute over the INF treaty banning nuclear medium-range missiles. Photo: Kay Nietfeld/dpa

18 January 2019, Ukraine, Kiew: Heiko Maas (SPD, l), Foreign Minister, is received by his Ukrainian counterpart Pawlo Klimkin at the Ukrainian Foreign Ministry. The main topics of the trip are the Ukraine crisis, the peace efforts in Syria and the dispute over the INF treaty banning nuclear medium-range missiles. Photo: Kay Nietfeld/dpa

18 January 2019, Ukraine, Kiew: A German (r) and a Ukrainian flag stand on the name tags of Heiko Maas (SPD), Foreign Minister, and his Ukrainian counterpart Pawlo Klimkin in the Ukrainian Foreign Ministry. The main topics of the trip are the Ukraine crisis, the peace efforts in Syria and the dispute over the INF treaty banning nuclear medium-range missiles. Photo: Kay Nietfeld/dpa

18 January 2019, Ukraine, Kiew: Heiko Maas (SPD, 3rd from right), Foreign Minister, will be received by his Ukrainian counterpart Pawlo Klimkin (3rd from left) at the Foreign Ministry together with the delegations for a discussion. The main topics of the Maas trip are the Ukraine crisis, peace efforts in Syria and the dispute over the INF treaty banning middle-range nuclear missiles. Photo: Kay Nietfeld/dpa

18 January 2019, Ukraine, Kiew: Heiko Maas (SPD), Foreign Minister, talks to journalists on the flight from Moscow to Kiev in the Airbus A321 of the German Air Force. The main topics of the trip are the Ukraine crisis, the peace efforts in Syria and the dispute over the INF treaty banning nuclear medium-range missiles. Photo: Kay Nietfeld/dpa

18 January 2019, Ukraine, Kiew: Heiko Maas (l, SPD), Foreign Minister, and his Ukrainian counterpart Pawlo Klimkin give a press conference at the Foreign Ministry. The main topics of the Maas trip are the Ukraine crisis, peace efforts in Syria and the dispute over the INF treaty banning middle-range nuclear missiles. Photo: Kay Nietfeld/dpa

18 January 2019, Ukraine, Kiew: Heiko Maas (l, SPD), Foreign Minister, and his Ukrainian counterpart Pawlo Klimkin give a press conference at the Foreign Ministry. The main topics of the Maas trip are the Ukraine crisis, peace efforts in Syria and the dispute over the INF treaty banning middle-range nuclear missiles. Photo: Kay Nietfeld/dpa

18 January 2019, Ukraine, Kiew: Heiko Maas (l, SPD), Foreign Minister, and his Ukrainian counterpart Pawlo Klimkin give a press conference at the Foreign Ministry. The main topics of the Maas trip are the Ukraine crisis, peace efforts in Syria and the dispute over the INF treaty banning middle-range nuclear missiles. Photo: Kay Nietfeld/dpa

18 January 2019, Ukraine, Kiew: Heiko Maas (l, SPD), Foreign Minister, and his Ukrainian counterpart Pawlo Klimkin give a press conference at the Foreign Ministry. The main topics of the Maas trip are the Ukraine crisis, peace efforts in Syria and the dispute over the INF treaty banning middle-range nuclear missiles. Photo: Kay Nietfeld/dpa

18 January 2019, Ukraine, Kiew: Heiko Maas (l, SPD), Foreign Minister, and his Ukrainian counterpart Pawlo Klimkin give a press conference at the Foreign Ministry. The main topics of the Maas trip are the Ukraine crisis, peace efforts in Syria and the dispute over the INF treaty banning middle-range nuclear missiles. Photo: Kay Nietfeld/dpa

18 January 2019, Ukraine, Kiew: Heiko Maas (l, SPD), Foreign Minister, and his Ukrainian counterpart Pawlo Klimkin give a press conference at the Foreign Ministry. The main topics of the Maas trip are the Ukraine crisis, peace efforts in Syria and the dispute over the INF treaty banning middle-range nuclear missiles. Photo: Kay Nietfeld/dpa

18 January 2019, Ukraine, Kiew: Heiko Maas (SPD), Foreign Minister, is going down the gangway of the Airbus A321 of the German Air Force after the flight from Moscow to Kiev. The main topics of the Maas trip are the Ukraine crisis, peace efforts in Syria and the dispute over the INF treaty banning middle-range nuclear missiles. Photo: Kay Nietfeld/dpa

18 January 2019, Ukraine, Kiew: Heiko Maas (SPD), Foreign Minister, is going down the gangway of the Airbus A321 of the German Air Force after the flight from Moscow to Kiev. The main topics of the Maas trip are the Ukraine crisis, peace efforts in Syria and the dispute over the INF treaty banning middle-range nuclear missiles. Photo: Kay Nietfeld/dpa

18 January 2019, Ukraine, Kiew: Heiko Maas (SPD, l), Foreign Minister, is received by his Ukrainian counterpart Pawlo Klimkin at the Ukrainian Foreign Ministry. The main topics of the trip are the Ukraine crisis, the peace efforts in Syria and the dispute over the INF treaty banning nuclear medium-range missiles. Photo: Kay Nietfeld/dpa