Britain's commitment to the Nato-led military action in Libya must not be limited by the public spending squeeze, Defence Secretary Liam Fox said today.
Chancellor George Osborne has signalled that the cost of the operations will be met from the Treasury reserve and was within the Government's military planning.
His initial estimate that the mission would cost only tens of millions of pounds may prove optimistic however, with the UK now preparing for a "long haul".
Giving evidence to MPs, Dr Fox said it was vital that Libyan dictator Muammar Gaddafi did not believe the financial plug could ever be pulled.
"It is very important that these issues are discussed but it is more important that we send a clear message in the current mission that we are not going to be limited by pounds, shillings and pence but we have the resolve to see through the mission.
"It is very important that we do not signal, at any point, that we may waver in our commitment to what we are trying to achieve in Libya," he told the Defence Select Committee.
Dr Fox said the UN-backed mission to protect civilians was "within the realms" of what had been envisaged under the Government's defence review which made swingeing cuts to the armed forces.
"Perhaps the level and speed and intensity has come earlier than we might have ever hoped but it has nonetheless fallen within the realms of what the SDSR was set up to be able to deal with.
"We believe it is sustainable and we believe we will have not only the military but political will to carry this through."
Quizzed at length about the operation, Dr Fox also denied that sending a group of expert British soldiers to Benghazi to help rebel leaders co-ordinating the response to Gaddafi's repression would open the way to arming the opposition forces.
"It is not a first step. We have been very clear that this is mentoring not training, nor is it intended to be," he said.
Great effort had been made to ensure they were not in a position where they could be taken prisoner by the regime forces as spies - although Gaddafi was "not rational", he said.
There were "plans to recover them if we believe the risk is increasing".
Dr Fox also gave his firmest repudiation yet of suggestions by US military chief Admiral Mike Mullen that the Libyan operation was at a "stalemate".
It was important not to extrapolate a bigger picture from events in a "fluid situation", he said - indicating that he had made his position clear at talks in the Pentagon yesterday.
"He was talking in the context of last week. Since then we have seen a number of factors move in favour of the coalition. I do not think we are in a position of stalemate. Politically, economically, militarily, we are moving forward."
The speed and scale of the degradation of regime military capability was "about as far from a stalemate as I could describe", he added.
Dr Fox also repeated his suggestion that Gaddafi and other regime figures should be aware their own lives were at risk if they operated at "legitimate" command and control targets.
He did not directly answer questions as to whether the dictator was being personally targeted but told the MPs: "We make very clear what the cause is and the people involved are very capable of understanding that."
The Ministry of Defence said UK and allied forces continued operating "at a high tempo" against regime hardware yesterday.
In an update on operations, Major General John Lorimer, spokesman for the Chief of the Defence Staff, said: "Nato's Operation Unified Protector, to protect Libyan civilians under threat of attack and enforce United Nations Security Council Resolution 1973, continued at a high tempo yesterday, with coalition air patrols over the areas around Misrata, Tripoli, Yafran and Brega.
"UK forces continue to play a key role in this activity providing strike, air-to-air refuelling and surveillance aircraft to the coalition as well as Royal Navy vessels to enforce the arms embargo.
"Yesterday, RAF Tornado and Typhoon aircraft successfully engaged two regime artillery pieces south of Zlitan and seven armed pick-up trucks near Misrata. A number of military vehicles at Brega were also destroyed."Reuse content