MANILA - Former Philippine leader Joseph Estrada, ousted in a popular uprising in 2001 and later convicted of graft, said Wednesday he would run again for president in next year's elections.

The announcement by the charismatic action movie star will excite his loyal fans, but observers said it was also likely to create constitutional controversies and dilute opposition efforts to oust the ruling coalition.

"Yes, I will run," Estrada, 72, told the Agence France-Presse, when asked to confirm local press reports of his decision.

A formal announcement will be made at the Catholic Sto Nino church in the impoverished Manila district of Tondo on Wednesday next week, Estrada said.

With its teeming slums, Tondo was the setting of many of Estrada's movies, in which he gained massive national popularity by playing tough guy roles, defending the poor and downtrodden.

Estrada said he was confident of victory, pointing out his experience climbing the political ladder from a town mayor to senator, vice president and eventually taking a landslide victory as the country's 13th president in 1998.

"I will not run for the presidency if I'm not sure I'll win," said Estrada, who is fondly called "Erap" by his fans, a play on the Filipino word "pare" which means "buddy".

Estrada's run in the May 2010 polls raises a series of constitutional and legal questions.

His six-year term was cut short half way through by a military-backed popular revolt, amid accusations he amassed wealth from illegal gambling kickbacks and shady deals worth about 80 million dollars.

He was convicted of large-scale graft and sentenced to life in jail in 2007.

President Gloria Arroyo, who played a key role in deposing him when she served as his vice president, pardoned him six weeks later.

But her legal aides said Estrada agreed to retire from public office when he was offered the pardon. The Philippines' constitution also bars presidents from serving more than one term.

Estrada -- who insists he was illegally deposed in a conspiracy led by Arroyo, the influential Roman Catholic church and businessmen -- said he was confident he would beat any legal challenge to his presidential bid.

"I commissioned some retired Supreme Court justices, deans of law schools and other legal luminaries, and they all agreed that I can still run," he said.

Estrada represents the United Opposition, a coalition of two influential parties that have been highly critical of Arroyo's regime.

However there are two strong opposition contenders representing other parties in next year's elections: Benigno Aquino, the son of late democracy icon Corazon Aquino, and billionaire property developer Manny Villar.

Defence Secretary Gilberto Teodoro will represent Arroyo's ruling Lakas-Kampi-CMD coalition.

Political science professor Ben Lim, from Ateneo de Manila University, said about 10 to 15 percent of the Philippines' 40 million voters were loyal Estrada fans.

But, with the president determined simply by whoever wins the most ballots in a single round of voting, Estrada's presence would likely be a filip for the ruling coalition, Lim said.

"Estrada will diminish the votes for the others (opposition candidates) in a field of several candidates," Lim said.

Arroyo could also set up legal hurdles in a bid to disqualify Estrada, citing the constitutional provision barring a president seeking re-election, according to Lim.

"But what is certain is that it will make politics exciting and entertaining," he said.

Estrada said he had picked Jejomar Binay, the popular mayor of Manila's Makati financial district and a prominent opposition leader as his vice presidential candidate.

Silvestre Bello, deputy secretary general of Arroyo's party, declined to comment on the chances of Estrada and Binay, "except to wish them well".