"The election of a new president must take place within 30 days of the post being vacated," Kanwar Dilshad, the election commission spokesman, told the AFP news agency.
Farhatullah Babar, a spokesman for the PPP, said: "The leaders [of the coalition] will discuss the post-Musharraf resignation issues, including the election to the presidency, the restoration of judges and the political situation."
The meeting will take place at the Islamabad residence of Asif Ali Zardari, widower of assassinated ex-prime minister Benazir Bhutto, Babar added.
Kamal Hyder, Al Jazeera's correspondent in Islamabad, said that in spite of Musharraf's resignation, Pakistanis remain uncertain about the direction in which their country is heading.
"The ruling coalition has been in agreement before, so the question is whether they can be in agreement again.
"The difference is the point of view of both parties. The PPP was very close to Musharraf at one time, when a deal was made with Benazir Bhutto.
"PML-N is trying to regroup and wants to see how the coalition government can bring back the judiciary within 72 hours," Hyder said, referring to a promise made to the sacked judges by the two coaltion leaders during polls.
"But Nawaz is an ally of Zardari and without each other they know they don't stand a chance, because other parties can also form a ruling coalition.
Mohammedmian Soomro, the senate chairman who also served as caretaker prime minister during emergency rule, is standing in as acting president.
Musharraf resigned after nine years in power to avoid the threat of impeachment charges, which followed accusations that he violated the constitution.
He said in a televised address: "After consultations with my legal advisers and close political friends, for the country and the nation today, I am deciding to resign from my office.
"I am leaving with the satisfaction that whatever I did for this country and the population, I did with honesty and commitment."
He is facing an uncertain fate, with officials from both the ruling coalition and the security services saying he could travel to Saudi Arabia in the coming days to perform Muslim rites.
A senior coalition official told the AFP that Musharraf would then head for the United Kingdom or Turkey.
His aides insisted he would return after his religious duties in the Gulf kingdom.
|Officials say Zardari, right, is too divisive a figure to become president [GALO/GETTY]
The government is considering a candidate from one of Pakistan's smaller provinces, election officials said.
They cited Sardar Ataullah Khan Mengal and Mehmood Khan Achakzai, both from Baluchistan. While Mengal is a Baloch, Achakzai is a Pashtun.
The coalition could also opt for a female candidate including the speaker of the national assembly, or lower house of parliament, Fehmida Mirza, the officials added.
But officials in the main coalition parties said Zardari, though powerful, is too much of a divisive figure to stand for the presidency.
Meanwhile the issue of the judges continues to plague the coalition.
It agreed in May to restore the judges - sacked by Musharraf in order to push through his allegedly unconstitutional re-election for another five-year term as president - but has failed to do so.
Divisions between the coalition partners, who bickered throughout the 1990s, could further threaten Pakistan's stability and even herald fresh elections as it combats a spiralling economic crisis and mounting Islamist resistance.
Zafar Jaspal, a professor of internal relations at Quaid-e-Azam University, told Al Jazeera on Tuesday that the biggest challenge for the coalition will be to hold it together in the coming days.
"The unifying factor between the main parties was Musharraf. They do not have a consensus on inflation and there is divergence of opinion on other issues. It is difficult to see how they will stick together," he said.
World leaders have urged Pakistan to place a premium on stability and unity following Musharraf's resignation.
"President Bush looks forward to working with the Government of Pakistan on the economic, political and security challenges they face," Gordon Johndroe, US National Security Council spokesman, said in a statement on behalf of the US.
Musharraf's opponents rejoiced nationwide after he announced his resignation, which many hope will bring an end to a year of political fighting that has largely paralysed Pakistan.
"Today we have buried dictatorship for ever"
Pakistan's prime minister
Stocks rose over four per cent as celebrations took place across Pakistan.
Special areas, some with wide screen televisions, were set up in several towns and cities for people to hear Musharraf's final address to the nation.
Some of the biggest celebrations were in Larkana, the hometown of Benazir Bhutto, the former prime minister who was assassinated in a suicide bombing in December.
In the northwestern city of Peshawar, near the country's tribal areas where Pakistani forces have been battling Taliban and al-Qaeda fighters, some people opened fire into the air and chanted anti-Musharraf slogans.
"The euphoria on the streets is quite evident. This is a man who became very unpopular," Kamal Hyder, Al Jazeera's correspondent in Islamabad, said.
Hyder said that the fact that the major coalition partners have been able to set their differences aside is a positive change in Pakistani politics.
"There will be an interim president until a president can be elected and of course this will be a president who will not have the sweeping power that General Musharraf had.
"This will also be a president who will give all the executive powers to the prime minister and of course who will return the sovereignty of parliament where it is supposed to be."