ISLAMABAD, Pakistan—With impeachment proceedings looming, the pressure on President Pervez Musharraf to quit built Friday as both his rivals and allies confirmed back-channel talks were under way that could ease him out.

Musharraf’s spokesman said reports the former army chief’s resignation was imminent were “baseless” but it was clear he has little support. The last of Pakistan’s four provincial assemblies passed a resolution against him and a key ally acknowledged the president lacks the support to survive a vote in parliament.

The political uncertainty adds to an already volatile situation in Pakistan. Officials said Friday that 10 days of fighting in a tribal region near the Afghan border have killed hundreds and displaced more than 200,000. It was one of the bloodiest episodes since Pakistan deployed troops along the border in support of the war on terror nearly seven years ago.

Coalition officials said they could present an impeachment motion to parliament as early as next week and the process could be over by month’s end. But officials in the president’s office say impeachment could drag on for months because the procedure is not laid out in the constitution.

Musharraf would be the first president to be impeached in Pakistan’s turbulent 61-year history. The party of ex-Prime Minister Nawaz Sharif, who Musharraf ousted in a 1999 coup, has even suggested he be tried for treason, which carries a maximum penalty of death. Sharif’s party is a partner in the ruling coalition.

Much depends on whether Musharraf decides to fight, and whether his rivals can stomach granting him immunity and the freedom to stay in Pakistan if he quits.

“There are a lot of background talks going on, whereby a way is trying to be found so that there is no impeachment,” Sen. Tariq Azim of the pro-Musharraf Pakistan Muslim League-Q party said Friday.

He said the president’s possible resignation, with legal protections, was an option, as was reducing the presidency to a figurehead role. However, coalition officials rejected the idea of trimming his powers, insisting Musharraf must go.

PML-Q secretary-general Sen. Mushahid Hussain said one possibility was that Musharraf would resign and be allowed to stay in Pakistan “in peace.”