Pakistan's ex-PM Benazir Bhutto has told the BBC talks with the government on brokering a power-sharing deal have stalled over "core issues".
Ms Bhutto currently lives in self-imposed exile in London
She said her Pakistan People's Party wanted any deal implemented before elections this year - not a "futuristic date" as suggested by the government.
Gen Pervez Musharraf, who is facing mounting opposition to his eight-year rule, is expected to seek re-election.
Violence from Islamist militants opposed to his rule is on the increase.
About 200 people have been killed in attacks since Islamabad's Red Mosque was cleared of militants in a bloody siege three weeks ago.
More than 100 people were killed as soldiers stormed the mosque.
'Rebalance of power'
In a BBC interview, Ms Bhutto refused to confirm reports that she had held direct talks with Gen Musharraf on Friday in Abu Dhabi, in the United Arab Emirates.
However, she did say that a series of high-level talks between her Pakistan People's Party and the government was aimed at arriving at a "transfer to democracy".
Ms Bhutto said she was seeking an atmosphere in which Pakistan's exiled political leadership - including herself - could return to the country.
Mr Musharraf is facing increased opposition and Islamist militancy
She said she was also calling for free and fair elections and a "level playing field" for all contenders.
In addition, she stressed the need to balance power between the presidency and the parliament.
Ms Bhutto said that she wanted any agreement implemented ahead of the forthcoming parliamentary elections.
Asked if Gen Musharraf had agreed to quit as head of Pakistan's military, she recalled his previous statements that he would "follow the constitution" and step down at the end of the year.
Ms Bhutto has previously said she has "very grave reservations" about a serving member of the military as president, saying it blurs the distinction between civilian and military rule.
Talks with government
The BBC's Ilyas Khan in Karachi says it is not clear whether Gen Musharraf has the full support of senior military figures for any deal which might be struck with Benazir Bhutto.
The president is scheduled to meet senior army figures in the next couple of days.
Our correspondent says the fact parliament is back in session means that any changes to legislation required by a deal could be pushed through.
Ms Bhutto has lived in self-imposed exile since leaving Pakistan in 1999, when Gen Musharraf took power in a bloodless coup.
She served as prime minister for two terms in the 1980s and 1990s, but was accused of corruption, along with her husband, charges which she says are politically motivated.
Ms Bhutto has been trying to engineer a comeback, but Pakistan's constitution would have to be changed to allow her a third term as prime minister.
Speculation is running high that Gen Musharraf may strike a deal with Ms Bhutto for her support in his re-election in exchange for allowing her return to Pakistan to run for prime minister.
Gen Musharraf has repeatedly rejected assertions by Ms Bhutto and another former prime minister, Nawaz Sharif, that they will return for the general elections due later this year.