GORI (Georgia)  - Moscow's military might was on display around Gori on Thursday as Georgian troops hoping to enter the strategically important town encountered formidable Russian firepower and had to retreat. Faced with Russian tanks and armoured vehicles, Georgian forces pulled back to positions along the road leading into the town, as expectations the Russian military would pull out proved premature. The situation was tense even on the road on the outskirts of the town. An AFP reporter heard a series of explosions and smoke was seen rising nearby. Explosions rocked the Russian-controlled Georgian town of Gori, posing a fresh threat to a fragile truce between the enemy neighbours. Georgia and the United States accused Russian forces of destroying installations in several towns as they withdrew. The Russian army retained Gori, halfway from Tbilisi and South Ossetia's main city, which has become the centre of the battle of wills over the French-brokered ceasefire agreed on Tuesday. A Georgian Interior Ministry spokesman said Russian forces were "destroying" Gori and laying mines and also demolishing installations in the Black Sea port of Poti. "They are destroying everything in Poti port... they are destroying the newly built roads in western Georgia," the spokesman added. A US official in Washington also said Russian forces were disabling Georgian military installations as they moved through the country. A senior Russian military official, General Vyacheslav Borissov, said it would take two days for all Russian troops to leave Gori. Russian President Dmitry Medvedev vowed that Moscow would act as a guarantor for the breakaway regions whatever they decide about their future, during talks with the leaders of South Ossetia and Abkhazia, who vowed to seek independence. Russian Foreign Minister Sergey Lavrov launched attacked the United States in a telephone conversation with Rice, saying Washington had to choose between a "relatively virtual" relationship with Tbilisi and a "partnership (with Russia) on questions that require collective action." Meanwhile, US Secretary of State Condoleezza Rice and President Nicolas Sarkozy agreed Thursday on the need for Moscow and Tbilisi to formally sign a ceasefire "without delay", the French presidency said Thursday. "The head of state and Mrs Rice both deemed that the six-point agreement protocol approved by Russian President Dmitry Medvedev and Georgian President Mikheil Saakashvili on August 12 must be signed without delay by the parties," it said in a statement. They called for the signature in order to "consolidate the cessation of hostilities and accelerate the withdrawal of Russian forces to their positions prior to August 7."