Possible Biden-Putin summit on the table as U.S. warns Russia preparing "full-scale assault" on Ukraine

Kyiv, Ukraine — U.S. President Joe Biden and Russian President Vladimir Putin agreed in principle on Sunday to meet, either in person or via video link, as diplomatic efforts to ease the crisis on Ukraine's borders took on new urgency with U.S. officials telling CBS News that Putin had ordered his troops to proceed with plans to invade. 

A U.S. official told CBS News that intelligence indicated Russian commanders had received orders to proceed with an invasion of Ukraine and were making specific plans for how to maneuver on the battlefield. The White House made it clear on Sunday that a Biden-Putin summit would not happen if Russia did invade Ukraine.

The Kremlin said Monday that it was "premature" to discuss any concrete plans for a summit, but confirmed that Putin was ready to meet Mr. Biden if the two countries' top diplomats are able to lay the groundwork.