Obama, who has been critical of Karzai, has been waiting for a new government in Kabul before announcing whether he will send tens of thousands of new troops to Afghanistan. The war has intensified and October was the deadliest month of the eight-year war for U.S. forces - yesterday the military announced that a soldier died Saturday of wounds suffered from a bomb attack while on patrol in southern Afghanistan.

Former Foreign Minister Abdullah Abdullah announced his decision to quit six days before the runoff election, after last-minute talks led by the U.S. and United Nations failed to produce a power-sharing agreement acceptable to Karzai, according to a Western diplomat.

In an emotional speech, Abdullah told supporters that he could not accept a runoff led by the same Karzai-appointed election commission that managed the fraud-marred vote in August. The runoff was set for Nov. 7 after U.N.-backed auditors disqualified nearly a third of Karzai's votes.

"I will not participate in the Nov. 7 election," Abdullah said, because a "transparent election is not possible."

The Obama administration, which had been critical of Karzai's leadership, appeared to accept the outcome.

Senior Obama adviser David Axelrod said that most polls showed that Abdullah would have lost the runoff anyway, "so we are going to deal with the government that is there."