By Margarita Antidze

TBILISI, Aug 14 (Reuters) - The United States will urgently press Russia to ensure free access to Georgian ports and the unfettered movement of ships from the ex-Soviet state, a senior U.S. envoy said on Thursday.

Matthew Bryza also told Reuters in an interview that Moscow should end its peacekeeping role in the Caucasus after siding with separatists in Georgia's rebel regions.

Bryza's comments came ahead of the arrival on Friday in Georgia of U.S. Secretary of State Condoleezza Rice, who the envoy said aims to build on a fragile ceasefire after six days of conflict between Russian and Georgian forces.

Russian troops have occupied parts of Georgia, including the Black Sea port of Poti, since repelling a Georgian attempt to seize back control of the separatist pro-Russian territory of South Ossetia, which threw off Tbilisi's control in the 1990s.

"We need to make sure that Georgia's transportation infrastructure is open, is not restricted by Russian ships in the Black Sea or Russian armour in Poti port, or near Gori," said Bryza, the U.S. State Department's envoy to the region.

Gori is a key Georgian town west of the capital Tbilisi, where Reuters witnesses saw Russian troops on Thursday.

"It's just bizarre that naval forces are blockading a sovereign independent country," he said. "I can't imagine how anyone who is sane could think that could be acceptable or reasonable."

The Russian General Staff said it was legitimate for "Russian peacekeepers" to be in Poti and Gori, as a French-led peace plan to stop the fighting allows Russian forces "to implement additional security measures" while awaiting international monitors.

Moscow has denied blocking oil shipments out of two Georgian ports but the Azeri state oil firm accused Russian warships of preventing a tanker with Azeri refined products from leaving Poti on Wednesday.

There have been no reports of a blockade at Batumi, Georgia's largest oil shipment port at the southern edge of the country's Black Sea coastline.

RICE VISIT

A BP-led group suspended oil flows to the Georgian port of Supsa and gas exports to Turkey via Georgia on Tuesday, citing security concerns. This forced BP to cut output from its huge oil fields in Azerbaijan. Traders estimate its markets are losing up to 1 million barrels per day in supplies.

Bryza said that during her trip Rice's priorities would be a viable ceasefire, restoration of security, the reopening of ports and the plight of people displaced by the fighting.

He also urged a rethink of peacekeeping in Georgia's rebel South Ossetia and Abkhazia regions: "I can't imagine how there could be any (Russian) peacekeepers (in the conflict zones)."

Some Western states have called for a multinational peace force to replace the Russian-dominated force in place since the regions broke away from Georgian rule in the early 1990s.

EU foreign ministers agreed in principle on Wednesday to send monitors to supervise a French-brokered ceasefire, but some remain sceptical Russia will withdraw so easily, with both regions firmly under Russian military control. (Writing by Matt Robinson; editing by Jon Boyle)

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