The United Nations is to investigate alleged irregularities in Afghanistan's presidential election.
Preliminary results are not expected for a few days
All allegations of voter fraud must be submitted in writing to the UN panel by 1430 GMT on Tuesday, organisers say.
The ruling means counting of ballots, which should have begun on Monday, cannot start until after that deadline.
One of President Karzai's main rivals, Yunus Qanuni, has vowed to accept the inquiry findings. Ink to stop multiple voting allegedly failed to work.
Speaking after talks with US and UN envoys, Mr Qanuni said: "To respect the will of millions of Afghans and to go along with our national interests I would accept the results of the election after the investigation."
He said he wanted the inquiry report published before the election results were announced.
Meanwhile, ballot boxes from the election have been pouring into counting centres across the country.
Afghanistan's Joint Electoral Management Body (JEMB) says ballot boxes in areas where complaints have been made will be separated from those from other areas.
Once they have been isolated, officials can start counting the rest of the votes.
The BBC's Crispin Thorold in Kabul says it may now take as long as three weeks for the full results to emerge.
Tuesday's deadline for complaints may have delayed the count, but work is still being done by officials to ensure that the number of votes cast tallies with the number of people eligible to vote.
Fears that militants linked to the Taleban would sabotage the vote appear to have been largely unfounded.
However, one person was killed in a rocket attack in the capital, Kabul, on Monday.
Correspondents say such attacks are common in Afghanistan, but rarely happen in the capital.
The United Nations helped organise Afghanistan's first mass democratic election.
Its three-member panel will comprise a former Canadian diplomat, a Swedish election specialist and a third member to be named by the European Union.
They will examine all serious allegations of malpractice at the polls - not just complaints from many areas that indelible ink aimed at stopping multiple voting could be washed away.
News of the ink problems on Saturday was swiftly followed by a boycott call from all of the candidates opposing Mr Karzai, a Pashtun who has led the US-backed administration in Kabul since the overthrow of the Taleban three years ago.
The indelible ink had to be applied to the cuticle of the fingernail
Vote organisers and observers have rejected calls for a new poll, saying it was reasonably democratic.
More than 10 million people were registered to vote, many of them refugees living in Pakistan and Iran.
Across Afghanistan, there was a huge enthusiasm for the vote, BBC correspondents reported.
The Taleban, however, called the election foreign-sponsored and vowed to continue their armed struggle.
Mr Qanuni, an ethnic Tajik, is the latest candidate to soften his stance on the boycott issue and say he will abide by the findings of the independent inquiry.
Shia Hazara leader Mohammed Mohaqiq and lone female candidate Masooda Jalal had already said they wanted a UN inquiry.
President Karzai, the favourite, criticised calls for a fresh election as an affront to the hopes of the millions of Afghans who braved bad weather and the threat of terrorism to turn out to vote.
And he was adamant there would be no back-room deals if he won the election - which he must do by a clear majority or face a run-off.
"If the Afghan people have voted for me - no horse-trading. The horse-trading times are over in Afghanistan," he told a news conference on Sunday.