By Zaffar Abbas BBC correspondent in Islamabad

There is likely to be a triangular contest in Pakistan's parliament on Thursday when the lower house meets to elect a new prime minister.

God willing, I will get the majority and we will form a government

Zafarullah Jamali

The two anti-government groups - Benazir Bhutto's Pakistan People's Party and the Islamic alliance - have fielded their own candidates after failing to reach an agreement.

But Zafarullah Jamali, the nominee of the pro-military Pakistan Muslim League, the PML-Q, is likely to be elected as premier.

His party has already demonstrated that it has a clear edge over its rivals by winning the post of National Assembly Speaker on Tuesday.

He stands the best chance of being elected as the leader of the house - who will then be sworn in as the new prime minister.

House support

Mr Jamali, 58, would be Pakistan's first prime minister to come from the province of Balochistan.

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But it may not be such smooth sailing for the PML-Q on Thursday.

To become prime minister, a candidate requires the support of more than 50% of the entire house, or at least 172 votes.

Although a number of smaller groups have extended their support, and there have also been defections in opposition ranks, the PML-Q is still a few votes short of a clear majority.

A senior party member, however, said a few more opposition members had assured them of their support, and it may not be difficult for Mr Jamali to win the contest.

PPP surprise

Ms Bhutto's PPP, in a surprise move, has fielded a former minister from Punjab, Shah Mehmood Quereshi, as its candidate.

Makhdoom Amin Fahim had been its earlier nominee.

No explanation has been given for this change, but a party member privately said it seemed Mr Fahim did not want to stand in an election in which he is certain to lose.

The alliance of Islamic parties, the MMA, has nominated its senior member, Maulana Fazlur Rehman, as its candidate.