London, Aug. 14 : Russia continues to challenge the United States, and especially President George W Bush to "choose" between Washington''s relationship with Georgia and its future ties with Moscow.

The challenge was mounted as Russian troops in about 70 military vehicles left Gori and headed towards Georgian capital Tbilisi, located 50 miles away.

In appeared to be a calculated defiance of the US and the European Union, which mediated a ceasefire deal 24 hours earlier, reports The Telegraph.

It maybe recalled that Bush had warned that the Russian advance could damage ties between the two countries, and demanded that Moscow "keep its word" over the ceasefire.

Bush also announced that he was sending a large US aid mission to Georgia.

Russian Foreign Minister Sergei Lavrov countered by saying: "We understand that this current Georgian leadership is a special project of the United States, but one day the United States will have to choose."

Britain''s Foreign Secretary David Miliband said: "Russian incursions into Georgia from South Ossetia or from Abkhazia are contrary to international law. The sight of Russian tanks rolling into parts of a sovereign country on its neighbouring borders will have brought a chill down the spine of many people, rightly."

Georgian President Mikhail Saakashvili has berated his country''s western allies for lack of assistance in the conflict.

But following Mr Bush''s offer of humanitarian aid, he claimed that Georgia''s ports and airports would be placed under US military protection, a suggestion quickly denied by the Pentagon.

Russian forces on Wednesday entered the main port at Poti and detonated explosives on three Georgian patrol vessels.

In and around Gori, several reports suggested Russian forces backed by South Ossetian militias were engaged in looting and violence, but Moscow denied the claims.

The ceasefire brokered by the EU on Tuesday called for Russian and Georgian forces to return to positions they occupied before hostilities began, obliging Russian troops to withdraw to from Georgian territory beyond the breakaway regions of South Ossetia and Abkhazia.

But though President Dmitri Medvedev officially signed up to the deal in Moscow, Russian forces on the ground appeared bent on crippling Georgia''s military capabilities for years to come. (ANI)