KABUL — Afghanistan's election commission proclaimed President Hamid Karzai the victor of the country's tumultuous ballot today, canceling a planned runoff and ending a political crisis two and a half months after a fraud-marred first round.

The Obama administration — which has been waiting for a government deemed legitimate to emerge in Kabul before announcing whether to deploy tens of thousands more troops — quickly commended the ruling.

"We congratulate President Karzai on his victory in this historic election and look forward to working with him" to support reform and improve security, the U.S. Embassy said in a statement. Britain and the United Nations also issued statements of congratulations.

The cancellation of Saturday's vote came one day after former Foreign Minister Abdullah Abdullah announced he was pulling out of the Nov. 7 vote. Abdullah said the ballot would not have been fair and accused the Karzai-appointed Independent Election Commission of bias.

The annulment is a huge relief to organizers who were scrambling to hold the election before the onset of Afghanistan's harsh winter, as well as to authorities who feared a wave of bloody violence on polling day after a Taliban spokesman threatened attacks against anyone who took part.

Election commission chairman Azizullah Lodin announced Karzai the winner during a news conference in Kabul.

"His excellency Hamid Karzai, who has won the majority of votes in the first round and is the only candidate for the second round, is declared by the Independent Election Commission as the elected president of Afghanistan," Lodin said.

Lodin said that the commission had the authority to make the decision because the Afghan constitution only allows for a runoff between two candidates. There is a chance that the ruling could be contested, but the international community came out strongly in support of it.

The U.S. statement said the commission's decision was in line with "its mandate under Afghan law."

A spokesman for Abdullah, however, said the decision did not reflect Afghan law but declined to say if the candidate would challenge it.

"The announcement that was made by the electoral commission today will not solve the problems of Afghanistan, and it doesn't have any basis in law," Fazel Sancharaki said.

He said Abdullah would give his reaction in a speech Tuesday. "We expected that this commission would announce something like this because this commission has never been independent and has always supported President Karzai," Sancharaki said.

Ronald Neumann, a retired U.S. ambassador to Afghanistan, said canceling the runoff was the country's best available option and that few were likely to contest the decision.

"It's over. He withdrew. Karzai wins. I think we are much more hung up than they will be on rules," Neumann said.

Karzai has led Afghanistan since U.S. forces invaded to oust the Taliban in 2001.