The US special envoy to Afghanistan has said it is reasonable to hope for fewer irregularities in the presidential run-off poll than in the August election.
Richard Holbrooke told reporters that one reason was that this time there were only two candidates - President Hamid Karzai and Abdullah Abdullah.
The run-off was called after no overall winner emerged from the first poll.
But Mr Abdullah now says he will pull out of the 7 November vote unless poll officials are dismissed.
Mr Abdullah's spokesman said the officials from the government-appointed Independent Election Commission (IEC) should be replaced by people who both Mr Abdullah and President Karzai found acceptable. Mr Abdullah, a former foreign minister, has previously accused the commission of not being impartial.
At a state department briefing in Washington, Mr Holbrooke said: "It is reasonable to hope that there will be less irregularities this time for several reasons.
"One, there are only two candidates. Two, there is the experience factor. Three the international community... are going to go all out to help make this a success."
Mr Holbrooke insisted his relationship with President Karzai was fine and that if he was re-elected, the US looked forward to working with him.
Initial election results from August suggested Mr Karzai had received 55% of the vote, and Mr Abdullah 28%.
But a UN-backed Electoral Complaints Commission (ECC) deducted hundreds of thousands of votes from the main candidates amid widespread fraud allegations.
This meant Mr Karzai's total was reduced to below the threshold required for outright victory - 50% plus one vote - indicating a second round was needed.
