Pakistan's main opposition alliance has announced a parliamentary boycott in protest at President Pervez Musharraf's plans to run again for office.
Opposition leaders say the election is illegal
The alliance said its members would resign from parliament and the four provincial assemblies on 2 October.
It made the announcement on the day Gen Musharraf registered for the ballot. The Supreme Court is to decide if he can run for president while army chief.
Earlier, the court ordered dozens of opposition members to be freed.
Gen Musharraf will stand down as army chief if he is elected for another presidential term, but, if not, he will keep his military post, his lawyers have said.
Pakistan's president is not elected by the people, but by a ballot of federal and provincial assemblies.
Earlier this week the United States called on Gen Musharraf to ensure the elections were free and fair.
He is a key ally in America's 'war on terror' but observers say Washington is worried about his declining popularity and the increasing problems of militancy in the country.
Opposition parties and lawyers have been campaigning to remove President Musharraf since he sacked the chief justice in March.
Gen Musharraf says he will stay on as army chief if he is not re-elected
"We have reached a consensus decision to resign from parliament," Maulana Fazlur Rehman, a leader of the powerful MMA religious alliance, told a news conference in Peshawar.
The MMA is a major part of the All Parties Democratic Movement (APDM) which was formed during protests earlier this year.
It is in power in North West Frontier Province and is a coalition partner in government in Balochistan.
The other main player in the APDM is the Pakistan Muslim League faction of exiled former Prime Minister Nawaz Sharif, whose power base is in Punjab province.
Alliance leaders say they will collect resignations from their members in the various assemblies and submit them on 2 October.
"On 2 October, the NWFP chief minister will ask the provincial governor to dissolve the assembly," Maulana Rehman said.
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The BBC's M Ilyas Khan in Karachi says the opposition resignations are not enough to pose a legal or numerical problem for Gen Musharraf's re-election - and will in fact make it easier for him to demonstrate a clearer margin of parliamentary support.
But the move may help erode the credibility of an electoral exercise already steeped in controversies, our correspondent says.
If MPs from the Pakistan People's Party (PPP) of Benazir Bhutto, another former PM, also resign, the election could become a farce, he adds.
The PPP is not a part of the main opposition alliance, and has been seeking a power-sharing deal with Gen Musharraf.
The Supreme Court's crucial decision on the legality of the president's re-election plans is now expected on Friday, observers say.
Opponents of Gen Musharraf want him out now
As well as Gen Musharraf, a retired judge filed his nomination for the presidential ballot on Thursday. Analysts say he has little chance of winning.
The PPP also nominated a candidate, who it says will run if the Supreme Courts bars Gen Musharraf from standing and the election still goes ahead.
Thursday's developments follow months of political uncertainty in Pakistan, with vocal opposition to military rule.
It is unclear what might happen if President Musharraf is not re-elected.
He appears set on keeping opposition protesters off the streets and critics say he is determined to cling to power, either as president or army chief, or both.