U.S. Vice President Joe Biden and Ukrainian President Petro Poroshenko have agreed that the future of sanctions against Russia must be linked to the full implementation of a peace agreement reached last month in Minsk.
The White House said Biden spoke with Poroshenko by phone on March 18.
"As long as Russia continues to fuel violence and instability in Ukraine, the international community must be prepared to increase the costs to Russia for pursuing such actions," it said in a statement.
Biden also welcomed the Ukrainian parliament vote on March 17 to confer special status on rebel-controlled eastern regions and grant them limited self-rule, but only after local elections are held under Ukrainian law.
Russia and the rebels reject that condition. Russian Foreign Minister Sergei Lavrov said on March 18 that the Ukrainian parliament had sought to "rewrite" the agreement reached on February 12 in the Belarusian capital.
In Kyiv, Prime Minister Arseniy Yatsenyuk said that no one on the Ukrainian side had much optimism that Russia "and the terrorists" would readily fulfill the Minsk plan.
Poroshenko signed the "special status" legislation on March 18.
Obama, Merkel Call
The White House said President Barack Obama and German Chancellor Angela Merkel also discussed the situation in Ukraine in a phone call on March 18.
The two leaders again agreed that there will be no easing of sanctions on Russia over its support for Ukrainian separatists until it has fulfilled all of its commitments under the Minsk agreement.
At a March 19-20 meeting in Brussels, European Union leaders could decide whether to extend sanctions targeting Russia's banking and oil sectors through December, when a key provoision of the Minsk deal is to take effect.
An EU diplomat speaking on condition of anonymity told RFE/RL that European Council President Donald Tusk is working with Germany and France on a proposal suggesting a decision should be made this month.
But diplomats said some countries, including Greece, Austria, and Slovakia, want to wait and make a decision in June, when some of the sanctions come up for renewal.
The Minsk deal calls for restoration of Ukrainian control over the state border with Russia in rebel-held areas by the end of the year under certain conditions.
Granting "special status" is part of a series of measures agreed to in the Minsk deal, which was brokered by German Chancellor Angela Merkel and French President Francois Hollande in talks with Poroshenko and Russian President Vladimir Putin.
It also established a cease-fire starting on February 15 and called for the withdrawal of heavy weapons far behind front lines in the conflict, which has killed more than 6,000 people since April 2014.
Fighting has decreased sharply but persists, with each side accusing the other of violations and Kyiv expressing concern the separatists may be using the truce to regroup for possible further offensives.
Ukrainian military spokesman Andriy Lysenko said on March 18 that one serviceman was killed and five were wounded in rebel attacks over the previous 24 hours.
"The enemy continues to strengthen covertly its groups near the separation line between opposing forces," Lysenko said in a televised briefing.
With reporting by RFE/RL's Rikard Jozwiak in Brussels, AFP, and Reuters