By Zaffar Abbas BBC correspondent in Islamabad

The three main parties in Pakistan have failed to reach a compromise deal on a future coalition government.

MPs are to elect the Leader of the House next week

As a result, all three have now filed nomination papers for their own candidates for the election of speaker and deputy speaker of the National Assembly.

The election for the two posts will take place when the lower house of the parliament meets on Tuesday.

Since none of the parties won a clear majority in the October elections, the speaker's election may give the first indication if any of the groups has the numbers to form a government.

Talks among the groups on forming a coalition went on late into the night on Monday, but there was no agreement.

Candidates galore

The main contenders, the Pakistan Muslim League (Quaid-e-Azam, or PML-Q) and the Pakistan People's Party (PPP), tried to woo the alliance of religious parties, the MMA.

Candidates for speaker

PML-Q: CA Hussain and Khursheed Kasuri PPP: Aitzaz Ahsan MMA: Liaquat Baloch

It seems neither main party was able to persuade the MMA leaders to withdraw their candidate for prime minister.

Now, all the three groups have put up their own candidates for the election of the speaker and deputy speaker of the National Assembly.

The PML-Q has nominated two candidates for the post of speaker.

Analysts say this indicates differences within the party, although the PML-Q has until tomorrow to withdraw one of its candidates.

Majority support

All the three groups have also nominated their candidates for deputy speaker.

The speaker's election is proving divisive

Former Prime Minister Nawaz Sharif's party, the PML (N), too has filed papers of its candidate, Sardar Yaqub Nasir, for the post.

Barring a last-minute compromise between any two of these groups, there is likely to be a three-way contest to elect the speaker and deputy speaker of the House.

The election is through a secret ballot, and a simple majority of the present number of the MPs (342) is required to determine the speaker.

The outcome will indicate the real strength of various groups in the National Assembly.

Later in the week, the Leader of the House will be elected by a show of hands.

To be elected, candidates need more than 50% of the total number of MPs, and whoever can demonstrate the support of the majority, will be the next prime minister.