U.S. President Barack Obama and German Chancellor Angela Merkel have spoken about the "significant increase in violence" in eastern Ukraine.
The White House said the two leaders spoke by phone on January 27 as Obama traveled back to the United States from a trip to India and Saudi Arabia.
The White House says Obama and Merkel agreed on the need to hold Russia accountable for its support for the separatists and failure to fulfill its commitments under a peace agreement.
And they discussed the importance of finalizing a "robust package of financial support" for Ukraine.
In recent weeks, the separatists have launched a series of new offensives along the Russian border.
Earlier on January 27, European Union leaders asked their foreign ministers to consider possible new sanctions on Russia in response to the rebel offensive.
A final decision to impose them is likely to be left to a summit next month.
The 28-member bloc has imposed a series of economic and political sanctions on Russia and officials linked with Russia's illegal annexation of Crimea last March and its support for separatists fighting government forces in eastern Ukraine.
The EU leaders' statement noted "evidence of continued and growing support given to the separatists by Russia" and said that support "underlines Russia’s responsibility."
The statement also urged Russia to condemn separatists' actions and to implement the September 2014 Minsk agreements, which include a cease-fire deal.
The EU leaders also condemned the killing of 30 civilians on January 24 through "the indiscriminate shelling of the Ukrainian city of Mariupol."
The United Nations said rockets fired from separatist-controlled territory into a residential neighborhood of Mariupol deliberately targeted civilians in an attack that violated international humanitarian law.
The shelling reignited fears the separatists would seek to seize the Azov Sea port city and push further toward the Black Sea peninsula of Crimea.
In Kyiv, Ukraine's parliament adopted a statement branding Russia an "aggressor state," a move that deputies hope will pave the way for punishment under international law.
The Verkhovna Rada also voted on January 27 to define separatist self-styled "people's republics" in the eastern regions of Donetsk and Luhansk as "terrorist organizations," and to appeal to the international community for additional nonlethal military aid and stronger sanctions against Russia.
Russian Deputy Foreign Minister Grigory Karasin called the Ukrainian statement "thoughtless and irresponsible," and said it was aimed at blocking efforts to end the conflict between government forces and pro-Russian rebels that has killed more than 5,000 people in eastern Ukraine since April.