Benazir Bhutto also claimed the United States and Britain had offered implicit support for her return to the country which she led twice before fleeing into exile in the face of corruption charges in the late 1990s.

Musharraf is facing opposition calls to quit amid mounting civil unrest highlighted by the military's storming of Islamabad's Red Mosque earlier this month to oust armed Islamists.

Asked on BBC radio if she had struck a deal with the military leader, Benazir said: "Not yet, no. There have been contacts and our contacts were over the holding of fair elections and a return to a political system in Pakistan.

"But ... over the months, nothing moved forward and we kept stumbling, for example we stumbled over electoral lists where 30 percent of the voters were disenfranchised and I felt that that didn't amount to a fair election.

"So we haven't yet reached any agreement although we've had a lot of discussion on the point."

The leader of the Pakistan People's Party (PPP) said she was now sceptical about striking a deal before Pakistan's elections.

"It's now three months left to the election so unless the regime acts rapidly it seems unlikely that there's going to be any agreement," she added.

Musharraf, the army chief who seized power in a bloodless coup in 1999, is constitutionally obliged to step aside as head of the military by the end of the year.