The British defense cuts are part of a broader drive by the coalition government led by Prime Minister David Cameron to reduce Britain’s annual government deficit of $240 billion, one of the highest deficits in Europe. The government is to provide details of its proposed cuts to Parliament on Oct. 20.

The cuts have set off a heated debate among Britain’s military services about what capabilities should be kept  and about the painful tradeoffs. British Army officers have questioned whether Britain should build two new costly aircraft carriers, and there have been fierce arguments about the cost of replacing submarines that carried nuclear-tipped Trident missiles.

“There is no way that the U.K., in the current financial climate, will be able to maintain a permanent at-sea, submarine-based nuclear deterrent, the size of fast jet fleet that we currently have, the ambition for a two-aircraft carrier strike program and an army of 100,000,” said Richard Dannatt, the former head of the British Army.

Adding to the quandary, the British Navy and Air Force can reduce spending by trimming weapons programs, while the army’s principal cost is personnel. The standing British Army has 103,000 soldiers, not including reserves or national guard troops, and army officers have argued that no more than several thousand could be cut without hampering the operation in Afghanistan, where about 10,000 British troops are deployed.

Longer-term plans call for shrinking the army by about 20 percent and establishing an army structure of five brigades and somewhat smaller airborne and commando units. That would enable Britain to deploy a 6,000-strong force for a prolonged ground operation, but the eventual size of the British Army has not been formally decided.

Whatever budgetary steps the British take have major implications for United States military planning. More than other allies, Britain has displayed both the will to join the United States in the initial phase of military operations and the wherewithal to quickly deploy, sustain and command its own forces.

“They have the capability to go in early on in a crisis, particularly on the ground, to be with us,” said a senior United States Defense Department official, who asked not to be named because of the confidential nature of the continuing consultations. “If they maintain the full-spectrum capability to operate with us quickly on the front end of a conflict, it is helpful. That is what we are watching and talking to them about.”