Britain is risking a new foreign policy rift with the US after bluntly telling the Bush Administration that it is “winning the battles but losing the war” in Afghanistan.

Gordon Brown and David Miliband, the Foreign Secretary, fear that the US remains “fixated” by Iraq and is failing to address what they regard as the real front line in the war on terrorism.

Disagreement has surfaced already over the US military’s desire to spray opium poppy fields from the air with herbicide, as well as to continue its bombing strikes on Afghan villages, which Britain complains undermines its strategy of “winning hearts and minds”.

Other areas of contention include what Britain regards as Washington’s indulgent attitude towards Hamid Karzai, the Afghan President, who is accused of tolerating, even conniving with, widespread corruption inside his government.

One source said: “The Americans see a bit of military success in Afghanistan and think it’s all fine. They are blinkered by Iraq and this is becoming symptomatic of a lack of serious engagement on policy across the piste.”

Mr Miliband has instigated a strategy overhaul on Afghanistan which, although not a formal “review”, is causing alarm within a US Administration still smarting over Britain’s withdrawal of troops from Basra in southern Iraq this week.

Some US officials suspect that Mr Brown intends to slide out of the “bad war” in Iraq by concentrating on the “good war” in Afghanistan. They acknowledge that the Basra pullout was based on military advice but had still hoped that Britain would wait for General David Petraeus’s crucial progress report to Congress next week.

State Department and Pentagon officials have told The Times that Britain appears to “want rid of Karzai”, while others have complained through diplomatic channels about “mixed messages” coming from the Brown Government. The Foreign Office denies that it is seeking Mr Karzai’s removal, but diplomats admit that there is a “sharp difference of opinion with the Americans” about the Afghan President.

Mr Miliband has pushed Afghanistan up the policy agenda, choosing Kabul as the destination for his first trip abroad as Foreign Secretary in July. He wants to “step up the game” by building the strength of the Kabul Government and security forces, luring a broader range of Afghans into the administration, as well as tackling longstanding corruption surrounding the narcotics trade.

Some of the issues were aired this week by a team of Foreign Office and Ministry of Defence officials in Washington to discuss next year’s Nato summit, which is likely to be dominated by the mission in Afghanistan.

The US, which contributes more than two thirds of Nato’s military strength in Afghanistan, is frustrated by the British refusal to countenance air-spraying of opium crops, a key source of revenue for the Taleban. Helmand province, where 7,000 British troops are based, produced a record crop of poppies this year, the largest output anywhere in Afghanistan.

Rather than alienate locals, the British forces are keen to take the longer route of training Afghan anti-narcotics teams and persuading farmers to plant alternative crops.

The MoD disclosed that an 18-year-old soldier was one of the two who died when a roadside bomb exploded in Helmand province on Wednesday, making him the youngest British victim of the Afghan fighting so far.

The ministry said that the two men were Private Ben Ford, 18, and Private Damian Wright, 23, of the 2nd Battalion The Mercian Regiment. Private Ford, from Chesterfield, Derbyshire, was on his first overseas deployment after joining the Army in July 2005. He and Private Wright, from Mansfield, Nottinghamshire, died when their Land Rover was blown up while on patrol north of Lashkar Gah.

Major Paul Gilby, officer commanding C Company The Mercian Regiment, said of Private Ford: “Young on paper, in life he was mature beyond his years in attitude, bearing and ability.” His family said last night: “We are immensely proud of our son and know that he lost his life doing something he was proud to be part of and that he loved.”

A number of 18-year-old soldiers have died in Iraq.

Osama bin Laden plans to issue a video message addressing the American people on the sixth anniversary of the September 11 attacks, the US-based monitoring service SITE said last night. A notice announcing the video was posted on jihadist forums by the al-Qaeda network’s media arm.

Times Recommends

• Milk: do we need a dairy godmother?
• DIY: the women doing it for themselves
• First double portrait of Princes unveiled