Russia signed a peace deal to end the conflict in Georgia today but said "extra security measures" were needed before it could begin withdrawing its troops.
An attack on a key rail bridge, blamed by Georgia on Russian forces, forced Azerbaijan to suspended oil exports by railway to ports in western Georgia - a reminder of the sensitivity of the conflict in a key energy transit region.
President Dmitry Medvedev, working from the Black Sea resort of Sochi, added his signature to a French-led peace plan already endorsed by Georgia and by leaders of the two rebel regions at the heart of the conflict, South Ossetia and Abkhazia.
President George W. Bush, speaking in Texas, said it was a "hopeful step" but that Moscow must now pull its forces out.
But Russian Foreign Minister Sergei Lavrov said withdrawal would depend on extra security measures ordered by Mr Medvedev, the nature of which was not made clear.
Asked how long the withdrawal might take, Mr Lavrov told reporters: "This does not just depend on us" and blamed the difficult situation on the ground for delays.
The French-led agreement drafted this week authorises Russian forces to take extra security measures on a temporary basis pending the arrival of international peacekeepers - which requires a UN Security Council resolution.
Russian troops withdrew from an area 45 km (30 miles) from the Georgian capital this afternoon and a foreign military observer said it appeared a partial pullout might be under way, although that was not officially confirmed.
In a letter sent by Nicolas Sarkozy to Georgian leader Mikheil Saakashvili, the French President also said Russia must withdraw from all major towns in Georgia under a peace accord it has signed, despite conditions authorising "additional security measures."
"As I specified at our joint press conference in Tbilisi, these 'additional security measures' can only be implemented in the immediate proximity of South Ossetia to the exclusion of any other part of Georgian territory," read the letter, made public by Mr Sarkozy's office.
The United States demanded yesterday that Russia withdraw from Georgia immediately, accusing Moscow of "bullying" its tiny southern neighbour by sending in troops and tanks.
A simmering conflict between Georgia and Russia erupted into war nine days ago, when Tbilisi launched an assault to retake its separatist province of South Ossetia, prompting a crushing counter-offensive from Moscow, which supports the rebels.
Violence on the ground continued.
Georgia accused Russian troops of severing the country's main east-west train link on Saturday by blowing up a railway bridge in broad daylight. Russia's General Staff denied attacking the bridge, saying it regarded hostilities as over.
One end of the bridge, near the town of Kaspi, lay collapsed on the riverbank in a pile of rubble and twisted steel, Reuters television pictures showed.
"We are now in peacetime. Why should we be blowing up bridges when our job is to restore?" Colonel-General Anatoly Nogovitsyn, deputy chief of the General Staff, told a daily official briefing in Moscow. "This therefore can only be yet another completely unverified statement."
Azerbaijan said the destruction of the bridge had forced it to suspend oil deliveries to the Georgian Black Sea coast. A pipeline running from the Caspian Sea to Russia's Black Sea port of Novorossiisk currently remains Azerbaijan's only oil export outlet.
A Reuters television crew interviewed villagers who said men in military uniform arrived by jeep, uncoiled wires and detonated a device remotely to bring down the bridge, blowing out nearby house windows.
The villagers blamed Russian forces but the identity of the attackers could not immediately be verified. Irregular militias, based in South Ossetia, have also been operating against Georgian targets in recent days.
Enforcing any settlement will be difficult, given the extreme mistrust between the two national leaderships.
Mr Medvedev called for a stronger role for the Organisation of Security and Cooperation in Europe (OSCE) in the South Ossetia conflict zone. He said in a statement he had expressed the view in telephone conversation with Tarja Halonen, the president of
Finland, which holds the bloc's rotating chairmanship.
Russian Colonel-General Nogovitsyn said Georgian snipers were still shooting in South Ossetia and that Russian forces had engaged a "Georgian sabotage group" near the Roki tunnel, the main crossing point for Russian troops into Georgia.
Russian forces continued to move around in parts of Georgia far outside the separatist areas of Abkhazia and South Ossetia where they maintain peacekeeping forces.
In the Georgian Black Sea port of Poti, witnesses said Russian troops had carried off crates and equipment in trucks and helicopters from the port and airport.
"They carried out everything they could take," a local resident, Tengiz Khukhia, told Reuters. "They loaded it onto the helicopters and took it straight away."
The Kremlin has deployed warships, planes, tanks and troops against Georgia in the biggest Russian military operation outside its borders since the 1991 collapse of the Soviet Union.
Moscow says Mr Saakashvili started the hostilities and that it had an obligation to defend Russian passport-holders in South Ossetia against Georgian attack.
Despite the peace deal, a gulf still separates the two countries over the future of the rebel regions, which broke away from Georgia in the early 1990s and declared independence, albeit without international recognition.
Mr Bush echoed the Georgian position today, saying South Ossetia and Abkhazia were part of Georgia "and there's no room for debate on this matter".
But Mr Lavrov has already told the West to "forget about Georgia's territorial integrity", saying the facts on the ground dictate a different reality.
Russia says 1,600 civilians died when Georgia stormed South Ossetia, though the figure has not been independently verified. Georgia says at least 175 people have been killed and hundreds more injured. The figure does not include South Ossetia.
Reuters