The U.S. is calling on Russia to stop aircraft and missile attacks in a breakaway region of the former Soviet republic of Georgia.

The White House said President Bush discussed the situation with Russia's Prime Minister Vladimir Putin in Beijing, where both leaders attended the opening session of the Summer Olympics.

The U.S. is urging Russia to pull its combat forces out of Georgian territory, where the situation is verging on full-scale war. In a statement, Secretary of State Condoleezza Rice calls for an "immediate ceasefire," and asks Russia to agree to international mediation. She says she and other U.S. officials have been in touch with "the parties" to the conflict, but she doesn't elaborate.

In Moscow, Russia's foreign ministry says Rice had talked to Russian Foreign Minister Sergei Lavrov, who told her that Georgia must be persuaded to pull its forces out of the breakaway region of South Ossetia.

Georgia launched a surprise military offensive to retake the area earlier today, reportedly killing hundreds of people and triggering a counterattack from Russia. Moscow sent tanks across the border, and has reportedly bombed Georgian air bases.