KABUL - A U.N.-backed fraud watchdog said Friday it was close to a verdict in its probe of Afghanistan's presidential election, which could force incumbent Hamid Karzai into a run-off against his main rival.

Afghanistan has been gripped by uncertainty since the August 20 election, marred by allegations of widespread fraud.

The bitter process has sparked tension between Karzai and his Western backers and helped delay a U.S. decision on sending extra troops to Afghanistan at a time when the Taliban insurgency is at its fiercest.

The U.N.-backed Electoral Complaints Commission (ECC) watchdog has been sifting through piles of dubious ballots to determine if Karzai is the outright winner or faces a second vote against former foreign minister Abdullah Abdullah.

We are still working today, said Nellika Little, an ECC spokeswoman, adding that the commission was looking to issue its ruling around Saturday.

We don't want to rush it. There is a lot of work to do.

Karzai won 54.6 percent of the vote, according to preliminary figures.

If enough votes were disqualified to push his total below 50 percent he would face Abdullah in a second round -- barring possible legal steps to invalidate the decision or an Abdullah decision to withdraw.

The Washington Post cited officials familiar with the results as saying the investigation had already cut Karzai's vote tally to about 47 percent, a result that would trigger a runoff.

The ECC said it was investigating fraud complaints and it was too early to speak about any numbers before the process is over. We are not coming up with any figures, said Little.

Once it is done with its work, the ECC will send its verdict to the Afghan election commission.

If mandated, the second presidential vote would then be due within two weeks but the onset of the bitter Afghan winter, which makes much of the country impassable, could undermine the effort. Afghanistan's ambassador in Washington, Said Jawad, has said a second round of voting was likely.

In the United States, the controversy surrounding the vote has been a major factor in the Obama administration's review of its Afghanistan strategy.

General Stanley McChrystal, the U.S. and NATO commander in Afghanistan, has recommended sending an additional 40,000 U.S. troops beyond the 68,000 due to be in place by the end of 2009.

Abdullah has signaled his openness to a possible compromise while calling for a second round.

Should it go to the second round? My preference is going for the second round, he told reporters Thursday.
We are ready and I have not dismantled the infrastructure for campaigning though the campaign will be different this time and (under) any circumstances I will pursue the agenda for change.

(Editing by Jerry Norton)