KABUL, Afghanistan - The top U.N. official in Afghanistan has acknowledged "widespread fraud" in the disputed presidential election and rejected allegations from a former deputy that he covered up cheating to smooth the path to victory for President Hamid Karzai.

The remarks by Norwegian diplomat Kai Eide appeared designed to win back respect for both the troubled U.N. mission and the entire election process ahead of a ruling by investigators on whether fraud was extensive enough in the Aug. 20 balloting to require a runoff.

Eide's reputation was tarnished when his deputy Peter Galbraith alleged that the U.N. mission chief played down allegations of widespread ballot-stuffing by Karzai's supporters. Galbraith, the top-ranking American in the U.N. mission, was fired Sept. 30 by U.N. Secretary-General Ban Ki-moon after the widely publicized dispute.

A U.N.-backed fraud panel is expected to decide this week whether to throw out enough votes to require a runoff between Karzai and his top challenger, Abdullah Abdullah. Doubts about the U.N.'s neutrality could throw the panel's rulings into question.

It is a setback to hopes of the Obama administration and its international partners that the vote -- the first presidential election run by Afghans -- would restore legitimacy to a government plagued by weakness and corruption.

Karzai told a news conference that "confusion" over election results had been "created by Western elements in our country." He did not elaborate.

At a separate news conference, Eide said Galbraith's allegations were untrue in some cases and taken out of context in others. Eide was flanked by ambassadors from the United States, Britain and France in a show of international support for the U.N. mission and its embattled leader.

Eide said he could "only say that there was widespread fraud" and that "any specific figure at this time would be pure speculation" until the recount is complete.

Final results have been delayed by more than a month as a U.N.-backed panel set up as a check on the Afghan-appointed election commission examines complaints and suspicious votes. Though preliminary tallies show Karzai winning with about 54 per cent, enough Karzai ballots are suspect that the voiding of fraudulent votes could drop him below the 50 per cent threshold needed to avoid a runoff.

Last week, Galbraith said he was sticking by his allegations and said the election fraud had been "preventable."

Among other things, Galbraith complained that polling stations were allowed to open in areas that were insecure, raising the likelihood of fraud. Eide said military operations were launched in a bid to secure to open as many stations as possible so Afghans in those areas had the opportunity to vote.

Once the election results become clear, President Barack Obama is expected to complete a review of Afghan strategy and decide whether to accept a recommendation by his top commander here, Gen. Stanley McChrystal, for up to 40,000 more troops.

Among the options under review is a plan to maintain U.S. troop numbers at their current levels and shift the focus to missile strikes and special operations against al-Qaida leaders, including those sheltering in neighbouring Pakistan.