In the latest violence, the deputy governor of Afghanistan's Helmand province has been killed in a bomb attack on a mosque, officials say.

'Failing state'

The three reports have appeared two years after a road map for international assistance was agreed in London.

Oxfam said a "major change of direction... to avert a humanitarian disaster" in Afghanistan was needed.

In an open letter, Oxfam predicts a "humanitarian disaster" in the country, pointing out that millions of dollars of development aid is being wasted.

The charity says that the international approach towards Afghanistan is lacking in direction and is "incoherent and uncoordinated".

"There are very many factors to explain the increasing insurgency, and of course criminality and the role of warlords and drugs traffickers is very important," said Matt Waldman, policy advisor on Afghanistan for Oxfam International.

"But we also have to understand that recruitment is much easier when people are living in desperate circumstances," he said.

'Resurgent violence'

The two American-based reports also warned that a new approach was needed to prevent Afghanistan becoming a "failed or failing state".

The US Atlantic Council began its report with the words: "Nato is not winning in Afghanistan" and talks of a stalemate.

"Without urgent changes Afghanistan could become a failed or failing state," it said.

"If Afghanistan fails, the possible strategic consequences will worsen regional instability, do great harm to the fight against Jihadist and religious extremism, and put in grave jeopardy Nato's future as a credible, cohesive and relevant military alliance."

Britain's ambassador to Afghanistan, Sir Sherard Cowper-Coles has rejected the suggestion that Nato is not winning the battle with the Taleban.

He told the BBC that the security situation was mixed, with violence localised. "Nato's own figures show 70% of the violence occurs in 10% of the districts."

He said the authors of the Atlantic Council report "were guilty early on of excessive optimism - of naive idealism - and they are now connecting with some of the realities in Afghanistan".

On Wednesday another body, the American Afghanistan Study Group, warned that "resurgent violence, weakening international resolve, too few military forces and insufficient economic aid" were all contributing to the country's woes.

In a separate development, Canadian Prime Minister Stephen Harper told President Bush that his country's troops will not stay in Afghanistan unless Nato deploys a further 1,000 soldiers in the restive province of Kandahar, where there is currently a Canadian contingent of 2,500 troops.

Seventy-eight Canadian soldiers and one diplomat have been killed in Afghanistan since Canadian troops were deployed in 2002.

The Taleban have mounted a comeback in Afghanistan over the past two years.

The south of the country has seen the worst violence since the Taleban were thrown out of power in the US-led invasion of 2001.

The Nato-led force has almost 37,000 troops in Afghanistan.