A US navy warship arrived in Georgia's main Black Sea port of Batumi on Sunday with humanitarian aid as Russia ignored Western demands to remove its remaining troops from Georgia's heartland, Reuters reported.
Russia says the residual troops are peacekeepers needed to avert further bloodshed and to protect the people of Georgia's separatist, pro-Moscow provinces of South Ossetia and Abkhazia two days after Moscow said it had wrapped up its withdrawal.
On Georgia's main east-west rail line, a fuel train exploded on Sunday after apparently hitting a landmine.
The conflict erupted on August 7-8 when Georgia tried to retake South Ossetia. A Russian counter-offensive pushed into Georgia proper, crossing its east-west highway and nearing a Western-backed oil pipeline.
Russian troops also moved into Western Georgia from Abkhazia, another breakaway region on the Black Sea. Hundreds of people were killed, tens of thousands displaced and housing and infrastructure wrecked in the fighting.
In Batumi, 80 kilometers ( 50 miles) south of another port, Poti, where Russian troops are still present, the USS McFaul arrived with aid for the tens of thousands displaced by the conflict.
Underscoring US support for Georgia, two other US ships are due to follow the guided missile destroyer to the port. The US has already delivered some aid by military cargo plane but is now shipping in beds and food.
Russia's Black Sea fleet flagship vessel, the Moskva, is no longer in the same area, having returned to its base in Ukraine on Saturday, Russian news agencies reported.
Georgian officials were assessing the scale of the damage from the fuel train blast, which could potentially disrupt a key trade route for oil exports from Azerbaijan to European markets.
Prime Minister Lado Gurgenidze told Reuters by telephone: "The railway is vital not just for the Georgian economy but for the economy of neighboring countries."
The United States and Europe fear the continued Russian presence in Georgia will cement the country's ethnic partition, undermine President Mikheil Saakashvili's pro-Western government and threaten vital energy pipelines criss-crossing the country.
Particularly worrisome for Tbilisi and the West is a checkpoint set up at the port of Poti, which lies outside the security zone Russia says is covered by its peacekeeping mandate and is hundreds of kilometers from South Ossetia.
"Putting up permanent facilities and checkpoints are inconsistent with the (ceasefire) agreement," White House spokesman Gordon Johndroe said.
France, which helped broker the ceasefire, urged Moscow on Saturday to order its forces out of Poti as soon as possible.
The secretary of Georgia's National Security Council, Kakha Lomaia, told Reuters Tbilisi had reached a deal with Moscow for the withdrawal of the Russian soldiers from Poti on Sunday but Russian officials said they could not confirm this.
Though not Georgia's busiest port for oil, Poti can load up to 100,000 barrels per day of oil products, which arrive by rail from Azerbaijan. It is also the gateway for merchandise moving to Georgia, other Caucasus republics and Central Asia.
Lomaia called on Russia to release 12 Georgian soldiers he said had been taken to Abkhazia, saying this violated the terms of a prisoner exchange agreement mediated by France.
French President Nicolas Sarkozy's office said he and Kremlin leader Dmitry Medvedev had agreed on Saturday on the need to create an international mechanism under the auspices of the Organization of Security and Cooperation in Europe (OSCE) to replace Russian patrols in a buffer zone south of South Ossetia.
In a conflicting account, the Kremlin said replacing Russian peacekeepers was not discussed. Russia has earlier said South Ossetians and Abkhazians would only accept Russian peacekeepers.
Despite repeated demands for a complete Russian pullback to positions before the conflict, the West lacks leverage over a resurgent Russia whose oil and gas it sorely needs.
A US trade official said Russia's actions could affect its membership of the Group of Eight industrialized nations and its bid to join the World Trade Organization.
"That is all at risk now," US Commerce Secretary Carlos Gutierrez was quoted as saying by Germany's Der Spiegel weekly.
The US envoy to the Caucasus said Russia had inadvertently helped Georgia's bid for NATO membership with its actions. Moscow sees Georgia and other ex-Soviet republics as part of its legitimate sphere of influence and opposes them joining NATO.