ISLAMABAD - The party of former Prime Minister Nawaz Sharif was poised to quit Pakistan's ruling coalition unless judges ousted by ex-President Pervez Musharraf are reinstated by a Monday deadline, Sharif aides said.

A Sharif lieutenant also volunteered Sunday to contest the election for Musharraf's successor, raising the prospect of a divisive race against Asif Ali Zardari, the widower of assassinated former Prime Minister Benazir Bhutto.

Since forcing Musharraf to quit, Pakistan's coalition government has been split over who should replace him and how to reverse his most draconian actions.

The rift has Pakistan's voters and foreign backers worried that the government is too distracted to tackle rising Islamic militancy and serious economic problems.

Pervez Rasheed, a close aide of Sharif, said the party's leaders would meet Monday to decide whether to remain in the five-month-old coalition government or join the opposition.

"General opinion in the party is in favor of parting ways," Rasheed told The Associated Press.

Sharif set the Monday deadline on Saturday in response to the surprise announcement that federal and provincial lawmakers will select the new president on Sept. 6.

Musharraf purged the Supreme Court during a burst of emergency rule in November.

Zardari and Sharif pledged to bring back the judges quickly after routing Musharraf's allies in February elections.

But a debate on how to solve Pakistan's constitutional mess quickly bogged down in political calculations, including whether stalwart U.S. ally Musharraf should face trial.

Sharif, who accuses Musharraf of treason, says Zardari reneged on a written agreement to restore the judges within 24 hours of Musharraf's Aug. 18 decision to quit rather than face impeachment charges.

Zardari, head of the main ruling Pakistan People's Party, has accused the judges of being too political, and analysts say he may also fear that the justices could reopen old corruption cases against him.

Zardari on Saturday played down the importance of his agreements with Sharif.

"No contract is binding" in politics, he told the British Broadcasting Corp.'s Urdu language service. "There can be a rethink on anything."

He said his party would try to keep Sharif on board, but declined to predict when the judges would return.

Rasheed said Monday's party meeting would also discuss the race to succeed Musharraf.

Zardari announced his candidacy on Saturday and appears assured of victory.

Zahid Khan, a spokesman for the Awami National Party, the third largest in the coalition, said Sunday that his party had decided to support Zardari.

A major opposition party has also backed his candidacy, showing that Zardari can turn to new allies to keep control of the government and avert new elections, even if Sharif withdraws.

Javed Hashmi, one of Sharif's most senior lieutenants, volunteered Sunday to run against Zardari.

"I am also willing to contest the presidential election, but I am bound to obey what the party decides," Hashmi told the AP.

Sharif said Saturday that his party would only back Zardari for president if the post is stripped of key powers accumulated by Musharraf, such as the right to dissolve Parliament and appoint the chiefs of Pakistan's powerful military.

Pakistan's political uncertainty has deepened amid a growing conflict between security forces and Islamic militants.

Twin suicide bombers killed 67 people outside a weapons factory near the capital on Thursday. Since then, at least 50 people have died in clashes in the Swat valley and near the town of Hangu.

On Sunday, an official said the decapitated body of a man accused of spying was found in Bajur, a region next to the Afghan border where fighting in recent weeks has reportedly killed hundreds and prompted more than 200,000 to flee their homes.

Fazl Rabbi, a local security official, said residents found the body Saturday near the town of Khar, his head lying on his chest and a note in his hand saying "This is the fate for those spying on Taliban."