Secretary of State Condoleezza Rice is urging Russia to halt aircraft and missile attacks in Georgia’s breakaway region of South Ossetia and withdraw combat forces from Georgian territory.

Rice says in a statement that the United States wants Russia to respect Georgian sovereignty and agree to international mediation with Tbilisi in a bid to end the crisis in the former Soviet state that threatens to plunge the volatile region into full-scale war. In Moscow, officials say Rice spoke with Russian Foreign Minister Sergei Lavrov about the matter.

US-allied Georgia launched a surprise military offensive to retake South Ossetia earlier Friday. The assault reportedly killed hundreds of people and triggered a ferocious counterattack from Russia, which has sent tanks across the border and reportedly bombed Georgian air bases.