US President Barack Obama and German Chancellor Angela Merkel have spoken about their concern over a "significant increase in violence" in eastern Ukraine. Separatists have recently launched a series of new offensives.
The White House said the leaders spoke by phone on Tuesday while Air Force One briefly stopped at an US base in Germany to refuel. The US president was returning to the States following a trip to India and Saudi Arabia.
Obama and Merkel reportedly agreed on the need to hold Russia accountable for its support for the separatists and its failure to fulfill commitments under a peace agreement.
The US President and the German Chancellor also discussed the importance of finalizing a "robust package of financial support" for Ukraine.
New financial assistance is currently being prepared by the International Monetary Fund (IMF).
On Tuesday, EU leaders also threatened new sanctions against Russia for its "growing support" for pro-Moscow rebels in Ukraine. The final decision about whether to impose them will be made at a summit next month.
In a rare joint declaration, leaders of the bloc's 28 countries called an extraordinary meeting of their foreign ministers to discuss Moscow's support for pro-Russia separatists in eastern Ukraine and the targeted attack on Saturday of the key port city of Mariupol.
"We condemn the killing of civilians during the indiscriminate shelling of the Ukrainian city of Mariupol on January 24, 2015. We note evidence of continued and growing support given to the separatists by Russia, which underlines Russia's responsibility," they said.
ksb/bw (AP, dpa)