British military commanders in Afghanistan who have been clamouring for more helicopters since the operation in Helmand province was launched in 2006 are to have their appeals anwered at last.

Seven Merlin helicopters are to be moved from Iraq to Afghanistan when the British troop presence in Basra is wound down by the end of July. The deployment of the helicopters is part of a package of reinforcements which could raise British troop numbers in Afghanistan by as much as 1,500.

There are no plans, however, to send an additional battle group of combat troops to take on the Taleban, according to senior defence sources.

While the US is due to send up to 30,000 more troops in an Iraq-style “surge”, Britain will focus on “thickening” its forces. This will involve more specialist troops, logistics units and new surveillance aircraft to seek out the roadside bombs that have caused 80 per cent of British fatalities.

The Merlins are being sent instead of Chinooks, despite previous plans to boost the size of the Chinook fleet in Afghanistan. Eight new Chinook helicopters, which have cost more than £500 million to buy and modify after a procurement calamity, are being delivered to the RAF from the end of this year, but will now stay in the UK, the sources said.

The new aircraft were originally bought for £259 million from Boeing in 2001 for the special forces in Iraq and Afghanistan, but have been grounded in climate-controlled hangars ever since because of rows over their airworthiness. They are now being reconfigured as normal utility helicopters at a cost of £215 million.

Keeping the Chinooks here will restrict the number in Afghanistan to ten. Like the Chinooks, Merlins are big helicopters but it will be their first venture in southern Afghanistan, an environment even more challenging than Iraq.

Whitehall sources said President Obama had not yet formally requested more British troops for Afghanistan, but Air Chief Marshal Sir Jock Stirrup, the Chief of the Defence Staff, has been indicating for some time that Britain would not deploy thousands more troops and that switching all 4,100 from Iraq to Afghanistan was out of the question. Nevertheless, under the current proposals, the extra equipment and the support units needed to operate them will help to build up the numbers.

The sources said it was likely that US combat medical teams would take the lead in the rescue of wounded soldiers in southern Afghanistan, which would reduce the burden for the RAF Chinooks, which currently carry out this role for injured British troops.

To cater for the influx of aircraft, American forces are going to build a second runway at the British Camp Bastion base, and a squadron of 120 RAF Regiment soldiers, currently in Iraq, is likely to be earmarked to protect the expanded airfield from attack by the Taleban.

Times Recommends

• 'New York has lost its edge'
• Copenhagen will fail – and quite right too
• More than 17,000 new underwater species found