Several thousand people gathered in the Georgian capital Tbilisi on Sunday to attend the first public meeting of a new movement led by billionaire and aspiring opposition politician Bidzina Ivanishvili.

Ivanishvili, whose wealth is estimated at $5.5 billion (3.5 billion pounds) by Forbes magazine, announced his political ambitions in October and called for the resignation of President Mikheil Saakashvili, the pro-Western leader of Georgia's 2003 Rose Revolution.

The congress of the public movement known as Georgian Dream was held in the capital's music hall and was attended by several stars of Georgian culture, art, and sports as well as former ministers and opposition politicians.

Ivanishvili's son Bera opened the event with a performance of his rap song Georgian Dream.

The country's leadership has completely exhausted ...and has become the main obstacle for society and state development, Ivanishvili senior, 55, told the meeting.

The time has come for all of us to wake up and to fulfil the Georgian dream, he said.

Saakashvili, 43, who swept to power on a wave of street demonstrations in 2003, has since faced down popular protests against his rule by opponents who accuse him of curbing freedoms in the Caucasus state, which is at a crossroads of oil links between the Caspian Sea and the West.

Analysts say Ivanishvili poses a credible threat to the government, partly due to his huge financial resources but also as he is untarnished by the political machinations of the past.

The businessman, whose banking-to-retail interests are mainly in Russia, has been denounced by the Georgian government as a Kremlin stooge and stripped of his Georgian citizenship.

The Justice Ministry ruled earlier this year that Ivanishvili's Georgian citizenship had become automatically invalid as he acquired a French passport -- a decision barring him from financing an official political party.

He was originally granted a Georgian passport under a presidential decree signed by Saakashvili in 2004, when he returned to Georgia from Russia. Georgia does not permit multiple citizenship.

The businessman also holds Russian citizenship, but says he is ready to renounce it as well as to sell his businesses in Russia -- including a chain of Russian drug stores and Moscow real estate.

Georgia's central bank in October launched a probe into a bank owned by Ivanishvili, and police have seized millions of dollars from its coffers on suspicion of money laundering.

Georgian soccer captain Kakha Kaladze, who attended the congress on Sunday together with Ukrainian soccer star Andrey Shevchenko -- said he had decided to quit the Georgian national soccer team in protest against the authorities.

(Reporting by Margarita Antidze; Editing by John Bowker)