No wonder this US soldier looks edgy, with green-on-blue attacks by Afghan forces increasing sharply in 2012.

US MILITARY CHIEFS and politicians have been thrown into turmoil by the latest killings of their soldiers at the hands of their erstwhile allies in the Afghanistan security forces.

They are at a loss to explain the vehemence and resentment which leads Afghan police and army to turn their guns on the Americans who are patrolling alongside them or even training them in military techniques.

US Army general Martin Dempsey has gone to Afghanistan to meet with officials to discuss how to stop this wave of attacks. This follows a meeting of top generals in the occupied country last week which discussed the dangers and damage to morale of these attacks.

The answers shouldn't be so difficult to fathom. A glance at Nato and US policies in the region provide an explanation. Drone attacks are a common occurrence especially in neighbouring Pakistan, where Obama's remote control weapons of mass destruction have killed thousands.

Air raids kill Afghan civilians on a regular basis. Every night US soldiers raid 40 Afghan homes looking for supposed 'terrorists. These raids are so unpopular that much of the job is now being handed to Afghan soldiers. Individual Nato soldiers have attacked Afghans. A US soldier is awaiting trial for the killing of 18 Afghans, mainly women and children. A British soldier has admitted bayoneting an Afghan child in the kidneys while hungover. The Islamic Koran was burnt at a US base, provoking angry demonstrations.

The US and western governments continue to back the corrupt and venal Karzai government. The Afghnas have now lived through 30 years of war and seen their living standards, life expectancy and education remain at the bottom of world rankings.

No wonder crisis point has been reached and green-on-blue attacks are Afghan soldiers and police turning their guns on Nato troops who are supposedly working with them and training them to take over in three years time.

The Western war in Afghanistan is sinking further into the mire as these attacks on troops mark a complete failure of the strategy put in place to allow eventual withdrawal on the West's terms.

The US soldier killed in southern Afghanistan yesterday on a patrol when one of the Afghans turned his weapon on the Americans is the latest in a series of 'insider' attacks.

Twenty US troops and one aid worker have been killed in the past two weeks, half of them shot by rogue Afghan soldiers or policemen.

The number of these green-on-blue attacks in 2012 is already higher than the total for 2011 -- 32 attacks resulting in 40 deaths, compared with 21 last year.

The US and Afghan authorities put the attacks down to Taliban infiltration of the Afghan security forces. This is worrying enough for them, showing much greater reach for the Afghan resistance than is often admitted.

One call is for greater vetting of new recruits. Another is a policy which now insists that US troops carry loaded weapons on them at all times, even when they are in US bases.

There is also a 'Guardian Angel' programme which effectively delegates one or two US soldiers to monitor Afghans in meetings and on patrols, preparing to shoot them if necessary.

But even more worrying for the US is the fact that only a minority of recent attacks have been carried out by the Taliban. Increasing numbers of attacks are on those forces training the Afghans -- with whom they supposedly have a closer relationship.

On the night of 10 August, three marines were killed by an Afghan policeman in Sangin, while a boy serving tea at a base 100 miles south killed three more marines only hours later.

To lose six Marines in one day to these attacks is a serious problem for the US. It points to the intractability of the situation in Afghanistan and the lessening of support for the occupiers 11 long years after the war began.

The war is unpopular at home, as Obama knows in election year, as well as in Afghanistan. What the generals and politicians know, but fear to admit, is that unless the troops withdraw and allow the Afghans to run their own country, they will need more than guardian angels in the future.