Election organisers on Monday declared Hamid Karzai president of Afghanistan for another five years, cancelling a run-off which threatened to descend into farce and further destabilise the country.

The announcement followed intense diplomatic pressure and sought to draw a line under two months of political chaos in a war-torn nation where 100,000 NATO and US troops are battling an increasingly virulent Taliban insurgency.

"We declare that Mr Hamid Karzai, who won the majority of votes in the first round and is the only candidate in the second round, is the elected president of Afghanistan," Independent Election Commission (IEC) chairman Azizullah Ludin said.

The president''s only challenger, former foreign minister Abdullah Abdullah, quit the contest on Sunday charging there were no safeguards to prevent a repeat of massive fraud that threw out nearly a quarter of votes cast in August.

UN chief Ban Ki-moon met Karzai and Abdullah amid a concerted diplomatic push to bring a quick end to chaos that has undermined Western efforts to cultivate democracy in Afghanistan eight years after a US-led invasion.