Pakistan's biggest party, the PPP, has nominated its leader, Asif Zardari, to be the country's president.
Pervez Musharraf resigned from the post on Monday in the face of the threat of impeachment by his political enemies.
Mr Zardari's main coalition partner, Nawaz Sharif of the PML-N, is not in favour of Mr Zardari getting the job.
They are also deadlocked over how many of the judges sacked by Mr Musharraf during emergency rule last November should be reinstated.
The PPP says it was the nomination of Mr Zardari was a "unanimous decision".
He took over as PPP leader after his wife, Benazir Bhutto was assassinated in December.
The president is chosen by the two chambers of the national parliament and the country's four provincial elections. The election will be held on 6 September.
Earlier on Friday, Mr Sharif agreed to let parliament hold a debate next week on how to reinstate the judges sacked by Mr Musharraf.
He previously threatened to pull out of the coalition government unless it was agreed on Friday that all the sacked judges be restored.
The PPP fears that if former Supreme Court judges, including ex-Chief Justice Iftikhar Chaudhry, are reinstated, they could overturn an amnesty that Mr Musharraf granted Mr Zardari Ms Bhutto last year which paved the way for them to return to the country.
That would leave open Mr Zardari to prosecution on long-standing corruption charges.
The coalition was elected in February, but analysts say there is a history of intense rivalry and mistrust between the two main parties.
Mr Musharraf, a key ally of President George Bush, stepped down this week after nine years in power to avoid being impeached.
He sacked about 60 Supreme Court judges during a state of emergency in November to prevent them from overturning his re-election as president.