The White House says President Donald Trump told Ukrainian President Petro Poroshenko the United States will work to end the deadly conflict near the Russian border in eastern Ukraine.
"We will work with Ukraine, Russia, and all other parties involved to help them restore peace along the border," Trump said in a statement issued on February 4.
The statement added that the two leaders discussed the possibility of meeting in the near future.
A statement by Poroshenko's office said the two leaders "noted the urgent necessity of establishing a complete cease-fire" in the region.
The Ukrainian president thanked Trump for his "strong support for the sovereignty and territorial integrity of Ukraine," the statement added.
The call came as an upsurge in fighting has killed at least 35 in a week of escalated fighting between Ukrainian troops and Russian-backed separatists in eastern Ukraine.
Ukraine has expressed concern that Trump could roll back some sanctions imposed on Russia after its illegal 2014 annexation of Ukraine's Crimea region and in retaliation for Moscow's military, economic, and political support for the separatists in eastern Ukraine.
Trump has repeatedly expressed hope for improved relations with Moscow. The phone call came a week after Trump spoke to Russian President Vladimir Putin.
On February 2, the new U.S. ambassador to the United Nations, Nikki Haley, expressed "strong condemnation of Russia's actions" in eastern Ukraine and warned that Ukraine-related sanctions against Russia would not be lifted until Crimea was returned to Kyiv.
"Crimea is a part of Ukraine. Our Crimea-related sanctions will remain in place until Russia returns control of the peninsula to Ukraine," she said.
At least 9,800 people have been killed since the conflict in eastern Ukraine erupted in April 2014.