KABUL: Taliban fighters warned Afghans not to take part in the war-wracked country's upcoming presidential runoff, threatening Saturday to launch a fresh wave of violence on polling day to stop them.

The warnings came on the first official day of campaigning for the Nov. 7 vote. The insurgents denounced the race between President Hamid Karzai and challenger Abdullah Abdullah as "a failed, American process" and said its fighters would "launch operations against the enemy and stop people from taking part."

The statement said Taliban militants will also cut off key roads and highways and warned that anyone who casts a ballot "will bear responsibility for their actions."

Taliban fighters killed dozens of civilians during the first round of voting Aug. 20, barraging several southern cities with rocket fire and cutting off the ink-stained fingers of at least two people who cast ballots in the militant-dominated south.

A spokesman for Karzai said his campaign is concerned about more violence during the runoff vote, but he said there is no other legal option and ruled out any sort of negotiated power-sharing deal.

"The only legal way to have a legitimate future government is to have elections," Waheed Omar said. "In our view that is the only constitutional way of putting an end to the current crisis."

Omar said there is some hope of avoiding a repeat of the violence that marred the August vote, noting assurances from Afghan and international forces that they can provide enough security. He called on the insurgents to let the election go forward without attacks "for the sake of this country."

Security fears are just one of the challenges that election officials face as they scramble to organize a new election amid a swelling Taliban insurgency before the advent of winter, which begins in much of the country around the middle of November, isolating remote villages and cutting off roads with snow.

Under intense U.S. pressure, Karzai acknowledged last week that he fell short of the 50 percent threshold needed for victory in the August ballot after U.N.-backed auditors threw out nearly a third of his votes because of massive fraud.

The Afghan Independent Election Commission, dominated by Karzai supporters, is under huge pressure to avoid a repeat of the cheating, which discredited the government and threatened to undermine public support for the war in the United States, which provides the bulk of the 100,000 NATO-led force.

As campaigning began Saturday, several senior Abdullah campaign officials accused the top three members of Afghanistan's Independent Election Commission of bias, saying they should be replaced to ensure the country's upcoming runoff is fair. A spokesman for the commission rejected the call.

Abdullah officials singled out election commission chairman Azizullah Lodin, chief electoral officer Daoud Ali Najafi, and the commission's deputy director, Zekria Barakzai. Abdullah's running mate, Homayoun Assefy, said the three were "openly working for Mr. Karzai" and should resign.

"If they are again in charge for the second round, the same thing will happen," Assefy said, referring to the widespread fraud. "If the second round is also controversial, then the result will not be good."

Assefy said the campaign was putting together a list of changes it would like to see in the runoff, including the changes at the top of the election commission.

"If none of our conditions are met, it will be sort of a boycott," he said, without elaborating.

Abdullah's campaign spokesman, Fazel Sancharaki, said the replacement of the officials would be a key condition that would be likely to prompt a boycott if ignored. Other officials would not confirm if the issue was a deal breaker for Abdullah.

Noor Mohammad Noor, a spokesman for the election commission, said the officials had been appointed by constitutional procedures and cannot be replaced.

"It is impossible. Everything has been set up already according to the constitution, according to electoral law, and they will continue their work," Noor told The Associated Press. "Karzai doesn't have the right to replace them, and neither does Abdullah."

Omar, the Karzai spokesman, declined to comment on the specific issue of bias on the election commission, but he said the Karzai team would back any reform that keeps the runoff from being as clouded in fraud allegations as the first round.

"We support anything that results in a more transparent election," Omar said.

The Obama administration is counting on a fair runoff to ensure the next government is legitimate. An outcome short of that is likely to raise further doubts about the wisdom of investing more U.S. troops and other resources in a counterinsurgency campaign in Afghanistan. A key pillar of that campaign is an Afghan government that is a credible partner of the U.S. and NATO.

In an effort to tamp down cheating, Afghan authorities have said they will cut about 7,000 of the 24,000 polling stations that they set up for the August ballot. Some of those stations were in areas too dangerous to protect. Others never opened, enabling corrupt officials to stuff the ballot boxes with impunity.

Before the election commission announced final results last week, Lodin met repeatedly with Karzai. At the time, his group was challenging the findings of the auditors on the U.N.-backed Electoral Complaints Commission, a separate body.

Lodin told The Associated Press that he saw nothing improper in those meetings and insisted he was not pressured to reject the auditors' findings. Lodin told reporters that despite control measures, however, there was no way his commission could guarantee a fair vote on its own.