Denis MacShane: The message Mr Cameron must deliver

Can Britain gently nudge the US to reduce the war-fighting profile of Nato troops in Afghanistan?

In 1951, a British Prime Minister flew to Washington and gently but firmly turned the US President away from his generals' desire to use nuclear weapons against China. In 1999, a British Prime Minister persuaded a US President to reject the caution of his generals and commit the US military might to bring an end to the genocidal decade of Serb militarism and wars in the western Balkans.

Tomorrow, a British Prime Minister is in Washington to meet a US President for the first bilateral since the election. Like Clement Attlee or Tony Blair, can David Cameron shape arguments and a strategic vision that help President Obama as well as Nato and the Euro-Atlantic community find a way out of the Afghanistan imbroglio? It is clear from talks with senior US officials – military, diplomatic, and foreign policy think tanks – that Washington is floundering in an intellectual swamp.

America, like Britain, has left Afghanistan policy to the generals. The pre-election briefing by the generals against Gordon Brown was a disgrace. The arrogance of General Stanley McChrystal about America's democratically elected leadership was revealed in Rolling Stone. The idolisation of generals and belief in the invincibility of Tom Clancy-style techno-military prowess is now over. General David Petraeus very sensibly fainted when he tried to explain to an increasingly sceptical US Congress his thinking on what to do in Afghanistan. With luck he will turn out to be an Eisenhower, not a Patton, and a politically savvy co-ordinator of different visions and interests. The Pentagon has to be persuaded that a US army of reconstruction is better than an army of occupation and permanent warfare.

After the bizarre episode of Britain's new Defence Secretary – "13th-century (Liam) Fox", as he is now known in military circles – rushing to Washington's neo-con Heritage Foundation to declare that British soldiers would be the last to give up being Taliban target practice, Mr Cameron has wisely decided that a new strategy is needed. Its prime aim is to reduce British casualties. The withdrawal from Sangin was a signal. No one doubts the bravery, honour and sacrifice of British officers and men. But patriotic admiration of our military is not enough.

Unfairly or not, Nato is seen as a Muslim-killing machine, and every dead Afghan civilian feeds another generation of young Muslims convinced by the rhetoric of Islamist jihad. China, Iran, Russia, Pakistan and India have no interest in helping Nato. Indeed, the weakening of the West is a desired policy objective of the non-democracies of the world.

That is why a number of European nations, every bit as committed to Nato and to a strong alliance with the US as Britain, have not sought to expose their soldiers either to killing Muslims or being killed. This is strategic common sense, not cowardice. Can Britain gently (and behind closed doors) nudge the US to reduce the war-fighting profile of Nato troops in Afghanistan? Al-Qa'ida has moved on to Yemen and North Africa, with its operatives appearing in Norway and Uganda. Democracy-hating militant Islamism does not need al-Qa'ida when London University can be a grooming ground for a young man ready to blow up himself and fellow passengers on a plane to Detroit.

This is not a policy of spineless scuttle. So far this century British prime ministers have followed, not shaped, global security policy decisions. The new Prime Minister is treading a careful path between the Heritage Foundation neo-con militarism of his Defence Secretary and his own instincts, which appear closer to Lord Salisbury's avoidance of disputes and wars when Prime Minister at the end of the 19th-century.

As in 1951 and 1999, a British Prime Minister has a chance this week to do some good and steer the US to the right strategic choice. That is what a real special relationship should deliver.

Denis MacShane is Labour MP for Rotherham and former Deputy Foreign Secretary