Afghanistan's election watchdog ordered that first-round results from more than 200 polling stations be dumped, leaving Karzai on only 49.67 percent of the vote.

The result is a huge boost to Karzai's main rival Abdullah Abdullah, who was sacked as foreign minister three years ago. Abdullah has capped a startling political comeback by depriving his former boss Karzai of his widely expected re-election.

The announcement came on Tuesday exactly two months to the day after the first round vote and follows weeks of political uncertainty at a time when Taliban strength is growing.

The chairman of the Independent Election Commission, Azizullah Lodin, said the commission, which organized the Aug. 20 vote, did not want to "leave the people of Afghanistan in uncertainty" any longer.

Afghan electoral law says a runoff is needed if no candidate gets more than 50 percent. Karzai accepted the commission's finding and agreed to a second round vote.

Karzai's acceptance has met with approval from the international community, including Germany.

A foreign ministry spokesman said, "It is important for all those involved to show responsibility, calm and moderation during the current situation and ensure there is a credible continuation of the electoral process."

Other world leaders have also praised Karzai's decision, including US President Barack Obama, NATO Secretary General Anders Fogh Rasmussen, UK Prime Minister Gordon Brown, and French President Nicolas Sarkozy.

bk/svs/AFP/Reuters/dpa
Editor: Michael Lawton