Philippines President Gloria Arroyo says she has decided to seek re-election next May, reversing an earlier decision not to do so.
Ms Arroyo swept into power in January 2001
Addressing a big crowd of supporters in her home province of Pampanga, Mrs Arroyo said she had deferred her retirement to deal with the country's pressing problems.
"I will run for president in the election of 2004. I will offer myself to the electorate in 2004," she said.
Her critics have said her initial decision to opt out was just a ruse to fend off opposition attacks.
Philippine law limits the president to only one six-year term, but Mrs Arroyo is not covered by this as she was not elected president.
As vice-president, she took the presidency in 2001 after her predecessor, Joseph Estrada, was ousted in an uprising sparked by a corruption scandal.
Her support ratings have risen since a failed coup attempt in July - although they have recently taken a battering because of corruption allegations against her husband.
The BBC's John McLean, in Manila, says the decision makes a big change to the political outlook for the Philippines because Mrs Arroyo has a good chance of winning the election.
The governing party has no other obvious candidate, our correspondent says.
Although Mrs Arroyo is trailing in the polls, she has the advantage of being the incumbent and another six years in office would give her more time to pursue her programme of reform.
She came to power promising a reforming government.
But since then, it has lurched from one crisis to another and problems such as corruption, crime, terrorism, communist and Muslim separatist rebellions, and especially poverty, remain virulent, our correspondent says.
Her announcement last December that she would not run for another term surprised analysts.
She said then that she "had to make this sacrifice" to bring an end to the divisive political manoeuvres that had paralysed her administration.
On Friday, Vice-President Teofisto Guingona - a long-time critic of the president - announced he was resigning from the ruling Lakas party.
He was the second leading party figure to quit in as many days.
Mr Guingona said in an open letter to Mrs Arroyo on Friday that he respected her earlier decision not to compete in the next elections.
He said he supported her decision to bow out, because she could then "focus on reforms badly needed by the nation".
"Unfortunately, those reforms have not materialised," he said.
Despite his resignation from Lakas, Mr Guingona will remain vice-president until the May elections.
On Thursday, senate majority leader Loren Legarda also said she was quitting the party to become an independent candidate in the elections.