Afghanistan was in political turmoil on Monday after the sole challenger to President Hamid Karzai quit a second round election amid uncertainty over whether it will stage a one-man contest in five days' time.
Two-and-a-half months after Afghans went to the polls to elect a president for the second time in history, Abdullah Abdullah announced Sunday he would not participate in the November 7 run-off, a move that should guarantee Karzai a second term in office but also threatens his legitimacy.
After Karzai snubbed a series of demands promoted by his rival as a chance to avoid a repeat of massive first-round fraud, Abdullah said he saw no point in standing, but stopped short of calling for a boycott.
The Independent Election Commission (IEC), whose leaders were appointed by Karzai, said the run-off would take place as scheduled on Saturday.
But Karzai opened the door to a possible solution in the courts and a UN spokesman conceded it was "difficult to see" how an election could take place with just one candidate, particularly with such a volatile security situation.
The commission is now expected to come under pressure to scrap the poll with the risk that turnout -- which was as low as five percent in some areas in the first round -- could sink to farcical levels.
"It's difficult to see how you can have a run-off with only one candidate," said Aleem Siddique, a spokesman for the United Nations mission in Kabul, which plays a major role in organising the ballot.
British Prime Minister Gordon Brown, who phoned Karzai after Abdullah's announcement, indicated that he did not want the president to simply claim the spoils of victory.
In a statement, Brown said he "hoped to see an Afghan government emerge that responds to the will of the people, that reaches out to all parts of Afghan society".
Insistent the first round fraud had been overstated, Karzai only agreed to a run-off under extensive diplomatic pressure.
But US Secretary of State Hillary Clinton said it was now up to the Afghan authorities "to decide on a way ahead that brings this electoral process to a conclusion in line with the Afghan constitution."
Following the widespread fraud in the first round on August 20, Abdullah demanded Karzai sack the IEC's head, Azizullah Ludin, and suspend four ministers who campaigned for the incumbent.
Snubbing his demands, but reacting to the withdrawal, Karzai's office said the president "regretted" the move but would "be obliged to follow" any ruling on the run-off from the election commission or the courts.
IEC chief electoral officer Daoud Ali Najafi said it was too late for Abdullah's name to be struck from ballot papers.
"We'll go for a run-off as scheduled," he said.
Karzai's share of the vote in the first round fell to 49.67 percent after around a quarter of all votes were deemed fraudulent.
Abdullah won just over 30 percent and would have had a mountain to climb to overhaul Karzai.