In a phone call with US President Joe Biden, Ukrainian President Volodymyr Zelensky called for a quick end to "aggressor" Russia.
"Just had a conversation with the US President. The American leadership on anti-Russian sanctions and defence assistance to Ukraine was discussed," Zelensky tweeted after the call.
"We must stop the aggressor as soon as possible," Zelensky added.
In a phone call on day six of Russia's invasion of Ukraine, White House officials said the two leaders spoke for "just over 30 minutes".
Violence has swept through Kyiv and Kharkiv in eastern Ukraine.