Efforts are under way to resolve confusion over whether the final round of Afghanistan's presidential election will go ahead on Saturday.
The planned run-off poll was thrown into doubt after opposition leader Abdullah Abdullah withdrew on Sunday.
The only remaining candidate, incumbent President Hamid Karzai, has said the Afghan Independent Election Commission should decide the issue.
The United States and the United Kingdom say it is up to the Afghan authorities to find a solution. They had previously supported a run-off vote, following the widespread fraud that marred the first round on 20 August.
However, the BBC reports they are now against it, given the danger to foreign and Afghan troops who would have to oversee the poll amid Taliban attempts to disrupt it.
Efforts are now under way to find a legal means of bringing things to an end, which could see the election commission calling off the vote and the Supreme Court ruling that Mr Karzai has won.
Dr Abdullah told the BBC he had made the decision "in the best interests of the country".
Earlier, he had told supporters his demands for ensuring a fraud-free election had not been met. However, he stopped short of calling for a boycott of the run-off vote.
Mr Karzai had rejected Dr Abdullah's demand that election officials who presided over the first round should be dismissed.
US Secretary of State Hillary Clinton said it was up to Afghan officials to decide the next step in the election process and urged Dr Abdullah to "stay engaged" and work for peace in Afghanistan.
British Prime Minister Gordon Brown said Dr Abdullah had pulled out of the election in "the interests of national unity."
Mr Brown said he told Mr Karzi it was now imperative that he formed an "inclusive administration" that could tackle corruption and build up popular local government.
Mr Abdullah polled second in the election on 20 August behind Mr Karzai. But the election was discredited after the United Nations threw out nearly a million ballots, one third of Mr Karzai's total, on grounds that they were fake.
The UN's Electoral Complaints Commission's action meant Mr Karzai's total was reduced to below the 50% plus one vote threshold for outright victory, indicating a run-off poll was required.