Benazir Bhutto is due to meet fellow Pakistan opposition leader Nawaz Sharif, to discuss a possible boycott of January's election.
Ms Bhutto has been campaigning in Pakistan's north-west
Mr Sharif has said his Muslim League will not take part unless judges sacked under emergency rule are reinstated.
He is expected to seek the same from Ms Bhutto, though she has said a boycott could legitimise President Pervez Musharraf's emergency rule decision.
He imposed the measures on 3 November, blaming militancy in the country.
He later defended his decision, saying it was taken "in the national interest" as Pakistan faced a crisis caused by militant violence and a judiciary which had paralysed the government.
Pakistan has been engulfed in political upheaval in recent months, and the security forces have suffered a series of blows from pro-Taleban militants opposed to Mr Musharraf's support for the US.
The meeting between Ms Bhutto and Mr Sharif in Islamabad will be the first since the two former prime ministers and former rivals returned to Pakistan after years spent in exile.
The BBC's Dan Isaacs in Islamabad says that the two leaders have an important decision to make - their participation in the elections will not only give the poll legitimacy, but also consolidate President Musharraf's role as civilian head of state.
Ms Bhutto has said her Pakistan People's Party would take part in the 8 January elections, but could still boycott them.
Speaking in Peshawar, Ms Bhutto said an opposition boycott of the polls would only help legitimise Mr Musharraf's imposition of emergency rule.
The vice-president of Mr Sharif's Pakistan Muslim League (PML-N) party, Tahmina Daultana, said Ms Bhutto should not take part in the elections.
"If she goes in and comes in through the back door, getting the support of President Musharraf, then that will not be a democratic way," he said.
Thousands of lawyers, judges and political opponents of the government were detained under the emergency, though the government says more than 3,000 detainees have now been freed.
Last week, after intense pressure from both home and abroad, Mr Musharraf said that he would end the state of emergency on 16 December, ahead of the polls.
He also stepped down as head of the army and was sworn in as a civilian president.
Correspondents say Mr Musharraf's Western allies, including Pakistan's main international backer the United States, want elections that at least appear to be free and fair, and an opposition boycott of the polls would be a severe blow to that.