Sri Lanka's former top General Sarath Fonseka, the architect of the military victory against the LTTE, has announced he will run for presidency in the January polls as the common candidate of the Opposition, setting the stage for an electoral battle with incumbent Mahinda Rajapaksa, another war hero.

"I am joining the race for Presidency," 58-year-old Fonseka, who resigned at the Chief of Defence Staff earlier this month following a spat with Rajapaksa over credit for the spectacular military win against LTTE, told a packed press conference in capital Colombo.

He said he would try to unseat President Rajapaksa as the joint candidate of the Opposition parties, including the United National Party (UNP) of former Premier Ranil Wickremesinghe, in the presidential polls to be held on January 26 next year, two years ahead of schedule.

Voicing confidence that he will win the polls, Fonseka vowed to abolish executive presidency. "The bane of the country is executive presidency and we will immediately, after my victory, will take action to abolish executive presidency," he said.

"And that (executive presidency) has done enough damage to the country... So the powers have been abused, specially at present all the powers are being abused and the executive presidency has to be abolished to ensure one man cannot run the country anymore."