KABUL - A U.N.-backed watchdog that has ordered a partial recount of Afghanistan's presidential election votes because of fraud allegations said on Monday it will allow small samples of ballots to be inspected to speed up the process.

The country has been in a state of political uncertainty since the August 20 poll, with accusations of widespread fraud delaying the announcement of a final result.

Preliminary results show incumbent Hamid Karzai winning in a single round with 54.6 percent, but if enough of his ballots are thrown out and bring his tally to lower than 50 percent, he would face a run-off against former foreign minister Abdullah Abdullah.

The head of the U.N.-appointed Electoral Complaints Commission (ECC), Grant Kippen, told Reuters he had agreed to a recount of a smaller sample to determine more quickly whether the fraud was large enough to force a second round.

...rather than look at all the ballot boxes and polling stations ... the approach going forward would be to take a sample of that total number and then work on that sample, Kippen said.

Sampling is a recognised standard and technique, an approach that is used in other places, he added.

The ECC said it has found clear and convincing evidence of fraud and ordered a recount of polling stations where suspiciously large numbers of votes were cast or where one candidate won more than 95 percent.

Kippen said the latest figures show the recount would apply to about 3,000 polling stations, 500 more than previously announced, or about 12 percent of the total.

Officials from the Afghan election commission say they are scrambling to carry out the fraud probe quickly, so that if a second round run-off is needed it can be held before winter makes it impossible.

Karzai acknowledges that some fraud took place in the poll, but says it was exaggerated by the Western media and international observers.

A European Union observer mission says more than a quarter of all ballots, including more than a third of those cast for Karzai, were suspicious.

(Editing by Jonathon Burch)