Biden, Putin Discuss Ukraine, Iran Nuke Deal During Tensed 2-Hour Summit

US says it doesn't know for sure what Russia intends to do in Ukraine, but is alarmed at the deployment of some 100,000 battle-ready Russian troops to the border.

Joe Biden and Vladimir Putin held a two-hour video summit Tuesday in which the US president said he would warn of painful sanctions and increased military support for Eastern Europe if Russia invades Ukraine.

"Greetings, Mr. President," Putin said in a brief video clip released by the Kremlin. Biden said it was "good to see" his Russian counterpart, adding that he hoped their next session would be in person.

Despite the friendly opening scene, the summit, lasting just over two hours, was steeped in tension.

Russia denies planning to invade Ukraine, but with satellite pictures showing massive troop concentrations on the border, fears are growing of war in Europe.