In this file photo an Afghan election worker carries a ballot box at an election commission office in Jalalabad east of Kabul. Picture: Rahmat Gul, File

Kabul -

Afghanistan is set to announce preliminary presidential election results on Saturday, with former foreign minister Abdullah Abdullah ahead in early counting but below the 50-percent vote required to avoid a run-off.

Abdullah secured 43.8 percent of the vote, with his main rival Ashraf Ghani on 32.9 percent, after four-fifths of ballots were counted, according to partial results released on Thursday.

The Independent Election Commission (IEC) said a press conference to release the full preliminary results was scheduled for 6.00pm (13.30 GMT).

The final official result is set to be announced on May 14 after a period for adjudication of hundreds of complaints over alleged fraud.

If no candidate gains more than 50 percent, a run-off between the two leading names is scheduled for May 28.

Ahmad Yusuf Nuristani, head of the IEC, has predicted that a second round vote would be likely.

Both Abdullah and Ghani, a former World Bank economist, have vowed to fight on if a run-off is required.

Another expensive and potentially violent election could be avoided by negotiations between the candidates in the coming weeks, but Abdullah has dismissed talks of a possible power-sharing deal.

"We have not talked or negotiated with anyone about forming of a coalition government," he told reporters after Thursday's batch of results.

Eight men ran in the April 5 election, with polling day hailed a success by Afghan officials and foreign allies as the Taliban failed to launch a major attack despite threats to disrupt the vote.

Serious fraud allegations are being investigated after the vote to choose a successor to President Hamid Karzai, who has ruled Afghanistan since the Islamist Taliban regime was ousted in 2001.

The 2009 election, when Karzai retained power, was marred by fraud in a chaotic process that shook confidence in the multinational effort to develop Afghanistan and also marked a sharp decline in relations with the United States.

Votes involved in alleged ballot-box stuffing and other cheating have not been counted, and Saturday's announcement is expected to be followed by fierce debate over disputed voting papers.

Preliminary results were delayed by two days due to fraud investigations, with officials vowing to sift out all suspect votes before they were counted.

Turnout from the election is set to be nearly seven million voters from an estimated electorate of 13.5 million - well above the 2009 figure.

The eventual winner will have to oversee the fight against a resilient Taliban insurgency as 51 000 US-led combat troops leave Afghanistan this year.

Karzai, who is constitutionally barred from serving a third term, pledged to stay neutral in the election.

But he was widely thought to have backed former foreign minister Zalmai Rassoul, who took just 11 percent of the vote on the partial count.

Rassoul could still play a key role in power-brokering before the next president is chosen, as could former Islamist warlord Abdul Rab Rasoul Sayyaf, who collected a significant seven percent of the vote on the partial count.

All leading candidates have pledged to explore peace talks with the Taliban and sign a deal with the US that could allow 10 000 US troops to stay on after this year on a training and counter-terrorism mission.

Karzai's surprise decision to refuse to sign the bilateral security agreement last year after agreeing to the draft text plunged relations between Afghanistan and its biggest donor to a new low.

The outgoing president has fought several bitter public disputes with Washington in recent years, underlining efforts to establish his reputation as independent nationalist leader despite relying on US aid and military power during his reign. - Sapa-AFP