Supporters of Afghan President Hamid Karzai have criticised a UN panel investigating claims of fraud in the presidential election, reports say, BBC reported.

The news came hours before the panel was expected to reveal that Mr Karzai did not get the more than 50% of votes needed to avoid a second round.

Mr Karzai says he won the vote outright but widespread fraud has been alleged.

The US says no more troops will be sent to Afghanistan until it is established that the government is legitimate.

White House Chief of Staff Rahm Emanuel told CNN TV it would be "reckless" to take such a decision without a thorough analysis of the new government.

Washington is debating a request for 40,000 more troops to be sent to boost efforts to fight Taliban and al-Qaeda-linked militants.