While Predator and Global Hawk drones cross the skies of Iraq and Afghanistan looking for insurgents or hunting for Osama bin Laden, thousands of kilometres away in Washington they have been dragged into a vicious turf battle.

Resurrecting tensions over US airpower that have lingered since the Korean war, the air force is pushing to become “executive agent” for drones – unmanned aircraft – that fly above 3,500 feet. The army, navy and marines oppose the move, which would make the air force responsible for the acquisition and development of unmanned aerial vehicles such as the army’s Sky Warrior.

As Gordon England, the deputy defence secretary, prepares to make a decision, air force and army officers are furiously lobbying Congress in preparation for a possible legislative battle. The stakes have risen dramatically as the use of drones has ballooned. Central Command, which oversees the wars in Iraq and Afghanistan, now operates about 1,000 UAVs.

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Aside from reducing military casualties, these roving eyes in the sky are becoming an indispensable tool for detecting insurgents planting the deadly roadside bombs that have become the biggest killer of US troops in Iraq.

“You can’t bring the soldier back to the farm once he has seen Paris,” says Colonel John Burke, the army’s former director of unmanned systems integration, to underscore the growing attractiveness of drones.

Their proliferation has intensified the Pentagon debate over how drones are acquired and operated. The air force says there is a need to streamline acquisitions to reduce cost and duplication, and for greater standardisation to improve interoperability and lessen the potential for mid-air collisions.

The air force argues, for example, that the Pentagon should have procured more Predators to deploy in Iraq and Afghanistan, rather than allowing the army to develop the Sky Warrior, which will not be deployed until 2009.

Air force officers add that a compromise joint approach reached several years ago when it unsuccessfully pushed for executive agency has hurt UAV development.

“We can’t afford to compromise any longer, particularly when ‘compromise’ comes at the cost of inefficiencies and with no benefit beyond assuaging ruffled parochial egos,” says Lieutenant General David Deptula, deputy air force chief of staff for intelligence, surveillance and reconnaissance.

But the army counters by questioning the air force’s record on acquisitions, stressing that Global Hawk and Predator have seen cost overruns, while other programmes such as refuelling tankers and search and rescue helicopter have been embroiled in controversy. It points out that its Sky Warrior programme has so far met cost and schedule goals.

“The ruffled feathers and parochial egos belong to the air force ... the marine corps, navy, special forces and army are co-operating across acquisition programmes, common ground stations and future programme development,” says a senior army officer.

“It is the air force that refuses to join the joint team, preferring to criticise others, disseminate misleading statements and independently lobby Congress for support they do not have in the Pentagon.”

Colonel Charles Bartlett, head of a special air force task force on UAVs, says the army, marine corps and navy have also experienced cost problems with weapons systems. He dismisses suggestions that the air force is the only service looking to Congress for help.

“All the services are representing their interests ... the army has worked the Alabama delegation as hard as the air force has worked the North Dakota and Ohio delegations,” says Col Bartlett.

While Richard Shelby, the Alabama Republican senator from Alabama, is concerned about the impact on Redstone Arsenal, which manages much of the army’s UAV work, Byron Dorgan, the North Dakota Democratic senator, wants to attract more work for Grand Forks air force base, partly to make up for the loss of four refuelling squadrons scheduled as part of the Pentagon’s base realignment across the US.

Tom Ehrhard, a UAV expert at the Center for Strategic and Budgetary Assessments, says the debate is a “fundamental doctrinal issue” about the current state of Goldwater-Nichols, the 1986 law designed to improve co-ordination across the branches of the military.

“The bid for executive agent authority is in part an indictment of current joint organisations,” says Mr Ehrhard. “What the air force is trying to get is supposed to be taken care of with existing organisations but it clearly is not.”

But some experts, including Pierre Chao at the Center for Strategic and International Studies, argue that it would be a “strategic mistake” to narrow competition for UAVs.

“If you think it is a young technology, that the Orville and Wilbur Wrights of the 21st century are running around in the UAV marketplace, then as messy as it makes the environment, is it far more strategically important to have lots of players, different patrons behind those players, and to keep stimulating the useful competition of ideas that a useful inter-service rivalry brings.”

The air force argues that executive agency is required to reduce the possibility of mid-air collisions. But army officials say there have been no complaints from commanders in the field about traffic problems. Col Burke says the argument is a “red herring”, stressing that there has only been one minor incident in recent years when small Raven drone crashed into a helicopter on the ground.

“We are very pleased at the low number of accidents, but that does not reduce the potential,” says Col Bartlett. “We will continue to flood the skies with UAVs.”

Another reason the UAV debate has stirred up passions arises from concerns that the air force could use executive agency – which would be limited to acquisitions and development – to edge towards gaining control of how drones are deployed and operated.

Mr Ehrhard says executive agent authority would not impact the employment of forces, since the joint force commander, such as the head of Central Command, and not the air force, decides when to allocate a UAV to any one of the services.

But experts concede that one side-effect of executive agency could impact the army’s ability to ensure access to the Sky Warrior. Loren Thompson, a defence expert at the Lexington Institute, says the air force has reservations about the army’s plan to tether the Sky Warrior to army units.

Gen Deptula says executive agency would not directly impact deployment, but he says the issue needs to be re-examined.

“I am forced to conclude that the army’s plans for their use dooms them to sub-optimal employment,” says Gen Deptula.

“I am not suggesting the air force be given the army’s theatre-effects-capable UAVs [such as the Sky Warrior]. What I am suggesting is that rather than tethering such high-value assets to ground forces that may not be in the hottest part of the fire, such UAVs should be available to the Joint Force Commander who needs them most, wherever that might be.”

The army argues that it is important to keep drones such as the Sky Warrior “organic” to the units that are deploying them for tactical missions. It says army commanders would not get sufficient UAV resources because there are more requirements for drones at the theatre level.

“The army wants to put assets where they are most responsive to make sure the capability is available and versatile,” says Col Burke.

Army officials also argue that operating drones from the battlefield reduces communications problems, and they balk at suggestions that they should be operated from the US. The air force operates many of its drones from Nevada, which it says reduces the number of troops placed in danger on the battlefield.

“Why does the army have to have organic control [leaving] a large footprint in harms way?” says Col Bartlett. “[The air force] can provide the same combat capability from Nevada that the army can provide on the battlefield.”

Richard Aboulafia, an aerospace expert at the Teal Group, says the debate poses a real dilemma.

“What the army suspects, rightly or wrongly, is ‘thank you for filing your flight access request. We will get back to you within a 48-72 hour period and make certain that there are no air assets. Thank you and this is not a recording,’” says Mr Aboulafia.

Mr England is expected to debate the issue later this month. But regardless of his decision, the battle is unlikely to end there. On Capitol Hill, some lawmakers have introduced legislation requiring the Pentagon to appoint an executive agent. And the House armed services committee has appointed a panel to examine the “roles and missions” of drones, which could have even wider ramifications for their operation.

Peter Singer, an expert on contemporary warfare at the Brookings Institution, says the military is just starting to grapple with some of the key questions surrounding UAVs, including whether they should be operated by pilots as the air force does, or by trained specialists in the army.

“The people who really need to be making the decisions ... are the very senior leadership in both the civilian and the military world, and yet you are talking about people who needed their grandkids to programme their VCRs,” says Mr Singer.

“The best result of the air force pushing [executive agency] right now is that it really does create a debate and forces the issue.”