TBILISI, Georgia -- Georgia said Friday that a Russian warning of possible military action to flush out Chechen rebels was a threat of aggression against a neighbor and could not be justified as part of the international anti-terror campaign.

Russia has pressured Georgia for months to take action against militants in the Pankisi Gorge, saying they use it as a base to launch attacks against Russia.

Russian Deputy Prosecutor Sergei Fridinsky said Friday that 300-400 rebels were believed to be based in the gorge at any one time and accused Georgia of supporting them.

Russian President Vlad-imir Putin on Wednesday issued an ultimatum to Georgia to take strong action against the rebels or face Russian involvement. Putin based his argument on United Nations resolutions on fighting terrorism that permit unilateral action.

In an official response Friday, the Georgian Foreign Ministry said the warning of military action was nothing but a "threat of Russian aggression against a neighboring sovereign state."

Georgian President Eduard Shevardnadze later sent a five-page letter to Putin, complaining about Russian attempts to turn Georgia into an "enemy."

"No such threat has come from Georgia in relation to Russia or will come," Shevardnadze said in the letter, which was released to the media.

Angry words have flown between Tbilisi and Moscow since late July, when Russia accused Georgian authorities of allowing a 60-strong band of Chechen rebels to cross into Russia. But even before that, tensions had been building steadily over Georgia's lawless Pankisi Gorge, where Chechen rebels and terrorists allegedly linked to the al-Qaida terrorist network had found refuge.