Abdullah Abdullah, Afghanistan's leading opposition candidate, has said the legitimacy of his country's new government is at stake because of what he described as "state engineered fraud" at the elections.
"I think if the process doesn't survive, then Afghanistan doesn't survive.
"Because what does that mean? The same sort of regime that crafted this massive, massive rigging will be imposed upon Afghanistan for another five years," he told The Daily Telegraph in an interview published on Saturday.
"On top of whatever problems this government, this administration had, there will be its illegitimacy."
Abdullah, the main rival to President Hamid Karzai, said he will exhaust all legal avenues to challenge alleged vote-rigging in the Aug 20 poll and if unsuccessful, would not recognise the elections.
"We will exhaust all legal avenues. But finally, if it worked, all well, if it didn't we will not accept the legitimacy of the process and then this regime will be illegitimate," he said.
The newspaper said Afghan election officials have drawn up contingency plans to deal with protests similar to those held in Tehran after Iran's disputed presidential elections in June.
The Afghan election watchdog has received more than 1,500 complaints, including more than 100 from the Abdullah campaign.
More than 160 have been judged "high priority", including allegations of ballot box tampering and ghost polling stations which could prove "material to the outcome".
A Western diplomat told the paper, "Abdullah is enough of a diplomat that he knows he cannot threaten protests while the count is under way, even if in political discussions he lets it be known that such developments would be difficult to stop."
Final results are not due until Sep 17. If a candidate does not win more than 50 per cent of the vote, the election will enter a second round run off, with the results expected in mid-October at the earliest.