World leaders have condemned Russia’s attacks in South Ossetia, warning Moscow that failure to withdraw risks damaging international relations.

The White House said Russia’s military action in the Georgia was “dangerous and disproportionate” and that any further escalation of the conflict could harm bilateral ties.

“We have made it clear to the Russians that this will have a significant long term impact on US-Russian relations,” Jim Jeffrey, deputy National Security Adviser, said.

In Britain, a spokesman for Gordon Brown said: "We are urging an immediate ceasefire to the fighting in South Ossetia and calling for a resumption of direct dialogue between the parties."

Bernard Kouchner, the French foreign minister who has been dispatched to the region by President Sarkozy, forecast a Balkan-style war if neither side backed down. He said that such violence was “unacceptable at the doors of Europe” and reminded him of “other recent conflicts that have torn our continent apart”.

John McCain, who has made foreign policy the centrepiece of his campaign and been a constant critic of Moscow, said: "Tensions and hostilities between Georgians and Ossetians are in no way justification for Russian troops crossing an internationally recognized border.”

Obama accused Russia of escalating the crisis “through it's clear and continued violation of Georgia's sovereignty and territorial integrity” and called on it to stop its bombing campaign.

Former Soviet bloc countries also rallied to Georgia’s cause. Polish President Lech Kaczynski said interference in domestic Georgian matters was “unacceptable and could lead to tragic consequences".

Ukrainian officials, meanwhile, warned that their country could bar Russian navy ships, being deployed off Georgia’s coast, from returning to their base in the Crimea.

Pope Benedict, holidaying in northern Italy, professed his “profound anguish” over the fighting, which has “already caused many innocent victims and forced a great number of civilians to leave their homes”.

“I invite the international community and the countries with most influence in the current situation to make every effort to support and promote initiatives aimed at finding a peaceful and lasting solution,” the pontiff added in his Sunday address.

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