A published report says the findings of a probe into fraud allegations in Afghanistan's August election will trigger a runoff between President Hamid Karzai and his closest challenger.

The Washington Post says the U.N.-backed Electoral Complaints Commission has reduced President Karzai's portion of the vote to 47 percent, less than the 50 percent he needs to win outright.

U.N. officials say official results from the August 20 presidential elections could be announced on Saturday.

Preliminary results released last month gave Mr. Karzai 54 percent of the vote.  His main challenger, former Foreign Minister Abdullah Abdullah had 28 percent.

Afghanistan's ambassador to the U.S. Said Tayeb Jawad said Thursday a runoff was a "likely scenario."

The Post quoted an American official saying runoff ballots listing Mr. Karzai and Mr. Abdullah have already arrived at the U.N. mission in Kabul and says the biggest challenge is security.

Also Thursday, Mr. Abdullah rejected rumors that he is seeking a power-sharing deal with Mr. Karzai, and the Afghan leader's aide told VOA that the president would not accept a coalition government.

Some information for this report was provided by AFP and Reuters.