Russian President Vladimir Putin reportedly called President Obama to discuss a diplomatic resolution to tensions over Russia’s annexation of Crimea, the White House announced on Friday.

According to a statement from the White House, Obama received the phone call from Putin after a dinner meeting with King Abdullah of Saudi Arabia. The White House did not confirm specific details of how the U.S. and Russia plan to compromise on Crimea, but noted that Obama was specifically concerned about Russian buildup of troops along the border and its lack of cooperation with the Ukrainian government.

“President Obama noted that the Ukrainian government continues to take a restrained and de-escalatory approach to the crisis and is moving ahead with constitutional reform and democratic elections, and urged Russia to support this process and avoid further provocations, including the buildup of forces on its border with Ukraine,” the statement read.

“President Obama made clear that this remains possible only if Russia pulls back its troops and does not take any steps to further violate Ukraine’s territorial integrity and sovereignty,” the statement continued. “President Obama reiterated that the United States has strongly opposed the actions that Russia has already taken to violate Ukraine’s sovereignty and territorial integrity.”

The White House confirmed that Secretary of State John Kerry is set to discuss a formal proposal with his Russian counterpart, Foreign Minister Sergey Lavrov in the future. No date has been announced for the meeting between Lavrov and Kerry, who has been accompanying Obama throughout his tour of Europe this week.