The Senlis Council said the United States and its allies need urgently to reassess their strategy in Afghanistan, where Nato forces are bracing for a major battle with insurgents as winter snows melt.

The report was released hours ahead of talks in London between Afghan President Hamid Karzai and Prime Minister Tony Blair, whose country is the second biggest provider of troops in Afghanistan.

"The international community has reached a tipping point in southern Afghanistan," said The Senlis Council's report.

"The anticipated major spring offensive by the Taliban against international forces requires an urgent reassessment of the international community's counter-insurgency strategy," it said.

The report warned that the cities of Kandahar and Lashkar Gah were in the Taliban's sights.

The United States, which ousted the Taliban following the September 11, 2001 terrorist attacks on New York and Washington, last year handed over overall control of military operations there to Nato.

Britain initially spearheaded the International Security Assistance Force (ISAF)'s move into the volatile south of the country, but has faced fiercer than expected Taliban resistance.

Concern is now mounting ahead of an expected Taliban offensive as the winter ends, with observers warning that military defeat in the south could threaten the political stability of the whole country.

The Senlis Council said the West, while still relying on military force, should provide better economic and humanitarian support for ordinary Afghans who it said had been "sorely neglected" over the last five years.

The report was entitled "Countering the Insurgency in Afghanistan: Losing Friends and Making Enemies."

"The military are doing an admirable job in a very hostile environment, but the political, development and counter-narcotics efforts of the international community are not having the necessary positive impact.

In some instances "those policies are acting to further inflame the insurgency," it warned.

"What is required is a very frank reassessment of the realities of the current insurgency dynamic, the declining credibility of the international community and an acknowledgement of the legitimate grievances of the Afghan people."

The Senlis Council said that humanitarian aid, development and institution-building have been under-funded and neglected since the overthrow of the Taliban.

"This is a blatant disregard of the established counter-insurgency theories, which advocate a complete package of diverse development based interventions such as medical assistance and education, in addition to the necessary military responses," said Norine MacDonald, the founding president of The Senlis Council.

The report said that Afghans had legitimate grievances with the international community, including the civilian death toll, forced poppy crop eradication, a lack of humanitarian aid and the perception that Karzai's government was a puppet regime.