Afghanistan's UN-backed Electoral Complaints Commission (ECC), publishing a report into mass allegations of vote fraud, on Monday ordered that ballots from 210 polling stations be invalidated.

The ECC said it found "clear and convincing evidence of fraud" at the polling stations, which were across the country.

The ECC said it ordered the Independent Election Commission (IEC), which is the final arbiter of the election results, "to invalidate a certain percentage of each candidates' votes in six separate categories."

The findings of the ECC's investigations into widespread fraud allegations in Afghanistan's August 20 poll could see the IEC forced to call a run-off between President Hamid Karzai and his main rival, Abdullah Abdullah.

Earlier report:

KABUL — A report into the mass fraud allegations that have tainted Afghanistan's presidential election is to be released on Monday with President Hamid Karzai under intense pressure to accept a possible run-off.

The results of investigations by the UN-backed Electoral Complaints Commission (ECC) will form the basis of a decision on whether Afghanistan can finally declare a new president or must go to the polls for a second time.

The paralysis since the August 20 election has angered Afghanistan's backers. Senior US officials now say a political resolution is essential if President Barack Obama is to authorise extra troops to fight the Taliban.

"We are going public at 5:00 pm (1230 GMT)," ECC spokeswoman Nellika Little said.

The report is expected to cut Karzai's lead from 55 percent in preliminary results, possibly triggering a run-off as the victor must have 50 percent plus one vote to form a new government.

"Karzai will come in with less than 50 percent," a Western official close to the process said.

The president and his cabinet are "bending in the right direction, towards accepting a run-off" after meeting Monday morning, he said.

"The consequences for Karzai (of not accepting the ECC findings) are disastrous. He can't take on the international community and expect continued support. It's just not going to happen."

Karzai's main rival, ex-foreign minister Abdullah Abdullah, has 28 percent and has spearheaded vote-rigging accusations against the president, once a darling of the West whose administration is accused of rampant corruption.

"Our information is that Karzai has fallen to 47 or 48 percent and that the election will go to a second round," Abdullah's campaign spokesman Sayed Aqa Sancharaki said.

"Our priority and preference is for a second round. If there is an attempt to delay the second round, there should be political justification for doing so, agreed to by all involved, otherwise it will be illegal and we will not support any violation of the law," he said.

The ECC is an oversight body charged with investigating fraud allegations that have plagued the August vote.

It reports to the Independent Election Commission (IEC), a body appointed by Karzai that will make the final announcement on the election's outcome. Officials say the IEC is legally bound to accept the ECC order.

An IEC official, speaking on condition of anonymity, said the commission had clawed back votes for Karzai, putting him close to 52 percent.

The IEC is widely regarded as pro-Karzai and diplomats have accused the body of delaying tactics aimed at giving the president more time to reach a deal with Abdullah, possibly on power-sharing, that would avoid a run-off.

"They have to do that deal, they have to avoid a run-off," said another involved Western official.

IEC spokesman Abdul Rahim Nawakhtyar said the commission needed "a day or two" to examine the ECC report -- which will include an order to cut candidates' percentages based on the level of fraud detected -- before making an announcement.

"We think that we might be able to make an announcement by Wednesday," he said.

Patience among Afghanistan's international backers has been wearing thin with the political crisis poised to head into a third month and Karzai under huge pressure to accept the results, officials and diplomats said.

White House chief of staff Rahm Emanuel and Senator John Kerry both said over the weekend that it would be "irresponsible" to send more troops to Afghanistan to fight the resurgent Taliban before the election is resolved.

"I think it would be irresponsible and... reckless to make a decision on US troop level if, in fact, you haven't done a thorough analysis of whether in fact there's an Afghan partner ready to fill that space," Emanuel told CNN.

Obama is considering a request from his military commanders for another 40,000 troops to boost the more than 100,000 already in Afghanistan under US and NATO command.

Emanuel's words echoed Kerry, chairman of the Senate foreign relations committee and a close Obama ally, who met Karzai and Abdullah in Kabul at the weekend.

Karzai's survival -- and that of his government -- depends on the continued support of the international community, which has poured billions of dollars in aid into the country since overthrowing the Taliban regime in 2001.