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 may delay announcing presidential election results as fraud complaints have yet to be processed, officials said Tuesday, though a run-off vote is expected to be held next month.

Full results from the April 5 election were released late last month, and the final declaration that was due out on Wednesday will factor in the outcome of weeks of deliberation over fraud allegations.

The preliminary results showed former foreign minister Abdullah Abdullah in the lead on 44.9 percent of the first-round vote, with ex-World Bank economist Ashraf Ghani on 31.5 percent.

None of the eight candidates appeared to have gained more than 50 percent, triggering a run-off between the two top names as Afghanistan undergoes its first democratic transfer of power.

“We are waiting to receive the conclusion (of the complaints commission),” Noor Mohammad Noor, spokesman for the Independent Election Commission, told AFP late Tuesday.

“The decision to announce or delay the final results depends on when we receive it, and details of the decision since we maintain the right to object to it.

“There is still a chance for the final results to be announced tomorrow, otherwise there will be a delay.”

The Independent Electoral Complaints Commission (IECC) said it expected to deliver its work shortly.

“If we need more time to finalise our work, it is for the sake of more transparency and to have a fair and just outcome,” its spokesman told a press conference in Kabul.

Afghan officials and Kabul-based diplomats say June 14 has been pencilled in for the head-to-head election to choose President Hamid Karzai's successor as US-led troops withdraw from Afghanistan by the end of the year.

On Sunday, Abdullah received a major boost with the endorsement of third-placed Zalmai Rassoul, a close ally of Karzai.

Rassoul was seen as the favoured candidate of the outgoing president, but his own campaign gained little momentum and he took just 11.5 percent in the first round of voting.

Another costly, and potentially violent, election could be avoided by deal-making in the coming weeks, and Rassoul's support for Abdullah increased pressure on Ghani to concede.

Karzai, who is constitutionally barred from a third term in office, has stayed publicly neutral in the election.

The United Nations' mission has welcomed Afghanistan's conduct of the vote but warned officials that they must address all fraud allegations openly.

The 2009 election, when Karzai retained power after defeating Abdullah, was marred by ballot-box stuffing in a chaotic process that shook the multinational effort to develop the country after the ousting of the Taliban regime in 2001.

The first-round election last month was hailed as a success, with turnout far better than in 2009 and the Taliban failing to launch a major attack despite threats to disrupt the vote.

A run-off vote in June - at the height of the traditional “fighting season” - could prove more difficult for Afghanistan's stretched security forces.

The eventual winner will lead Afghanistan into a new era as US-led NATO combat troops end their 13-year war against the Taliban insurgency and international aid money declines.