President Hamid Karzai, under intense global pressure, looked set to agree to a run-off in Afghanistan''s disputed election on Tuesday after a U.N.-backed panel rejected as fraudulent tens of thousands of his votes.

Official confirmation of a second round now depends of Afghanistan''s Independent Election Commission, which is assessing the U.N.-backed Electoral Complaints Commission''s (ECC) findings and using them to recalculate its original tallies for the poll.

The heavily disputed August 20 vote has fanned tension between Karzai and the West and complicated U.S. President Barack Obama''s decision on whether to send thousands more U.S. troops to Afghanistan to fight a resurgent Taliban.

The U.S. group Democracy International said the ECC report showed the number of votes invalidated by the U.N.-backed group pushed Karzai''s total below the 50 percent needed to avoid a run-off. Provisional results had given Karzai 54.6 percent.

If the election does go to a second round, analysts have said Karzai -- who is a Pashtun, Afghanistan''s largest ethnic group -- is likely to win, but the scale of fraud alleged in the first round may continue to cast a shadow over the legitimacy of his rule.

U.S. Secretary of State Hillary Clinton said she expected word from Karzai on Tuesday and hoped for a quick solution.