Hamid Karzai said he needed $15-20bn to stabilise his country

Hamid Karzai urged the international community to donate the money in an interview with BBC2's Newsnight programme.

"Our estimate of foreign aid for Afghanistan for the next five years or so is from $15bn to $20bn to enable Afghanistan to do very well economically," he said.

The money would also enable the country to "complete the job that we have on terrorism," he said.

If the Afghan economy could not be boosted, he said, its population would be forced to depend on poppies and the heroin trade for their living.

"That in turn will draw in the economy in Afghanistan, causing terrorism to benefit and also bring the addiction and the drug use to Europe," he said.

Taleban 'finished'

Mr Karzai disputed figures that opium production in Afghanistan had increased recently, despite UK-backed efforts to tackle it - but accepted it was still the world's biggest producer.

Mr Karzai, who is on a three-day visit to Britain, also denied that the Taleban was making a comeback in Afghanistan.

"The Taleban and their terrorist associates are defeated completely in Afghanistan... they're finished, they're gone, they're in hiding.

"Would a defeated person in hiding be able to regroup? No."

However, he conceded that individuals, or small groups of three or so people, were still capable of carrying out terrorist attacks.

Afghanistan is still the world's leading exporter of opium

On Wednesday at least 46 people were reported to have died in a battle between government forces and suspected Taleban militants in the south of the country.

It was the biggest such clash in more than a year. "A number of terrorists were arrested and killed," said Mr Karzai.

During his visit, the Afghan leader has met Prime Minister Tony Blair to discuss plans to draft a new constitution for Afghanistan, and efforts to eradicate heroin production in his country.

Mr Karzai also met Defence Secretary Geoff Hoon, who pledged more military support for Afghanistan, amid concern in Kabul that desperately needed funds and troops were being drawn away to Iraq.

On Friday Mr Karzai will meet the Queen.