Russian President Vladimir Putin called U.S. President Obama on Friday to discuss a resolution to the crisis in Ukraine.

The White House says Putin called Obama on Friday while the president was travelling internationally.

The White House says Obama urged Russia to offer a written response to a diplomatic resolution to the Ukraine crisis that the U.S. has presented. Obama and Putin agreed that Secretary of State John Kerry will meet with Russian Foreign Minister Sergei Lavrov to discuss further steps.

Obama says Ukraine’s government is pursuing de-escalation despite Russia’s incursion into Crimea. He urged Putin to support that and to stop building up troops on its border with Ukraine.

The call comes as Ukraine’s government and the West are concerned about a possible Russian invasion in eastern Ukraine.