Whitehall's spending watchdog today delivers a mixed assessment of the British Army's ability to perform in desert warfare.

The warning comes as reports from Washington suggest the UK is preparing to participate in a US-led onslaught against Saddam Hussein.

In a report into last year's Saif Sareea II exercise in Oman, the National Audit Office (NAO) lists a catalogue of equipment and hardware failures which undermined the force's performance.

The committee says that helicopters failed to perform as expected against the rigours of desert life - whilst self-propelled guns failed to discharge.

In the face of desert conditions, soldiers' boots fell apart and heavy lifting vehicles were beset by technological problems.

The problems affecting the Clansman radio system were so great that the watchdog concludes that it will be "incapable'' of operating in a real conflict.

Whilst the Challenger II main battle tank "worked well", it required substantially more air filters, road wheels and track pads than planned to keep it operational.

Troops manning the tanks discovered that the fine dust clogged up the air filters - resulting in them grinding to a halt in just four hours.

Following the discovery, some 55 tons of spare parts had to be despatched to the region.

The report also warns that "complexities in the scoping, costing and funding of the exercise led to difficulties in the planning process".

NAO chief Sir John Bourn said: "Exercise Saif Sareea II was a major success for the United Kingdom in demonstrating the Armed Forces' ability to conduct operations over long distances and in supporting important foreign-policy objectives.

"However, the exercise highlighted a number of problems that need to be addressed.

"In particular, the joint rapid reaction forces must be properly equipped to undertake expeditionary operations around the world; and the planning of such exercises needs to be reviewed if maximum value for money is to be achieved in future."

Saif Sareea II was the largest deployment of UK military forces since the Gulf War. Over 22,500 military personnel, 4,500 vehicles, 21 naval vessels and 93 aircraft were deployed to exercise with Omani forces.

The NAO estimates that the total cost of the exercise will be in the region of £83 million.

It concludes that the troops "gained valuable training experience from operating in a desert environment".

Ministers say the operation was vital to ensure that the UK's forces were prepared for any possible military action against Saddam Hussein.