Leading article: Libyan intervention needs to be guided by discretion

It is in danger of being seen not as a struggle for self-determination, but a Western-backed coup

In its earliest days, the military operation in Libya promised to rehabilitate the principle of humanitarian intervention. Here was a tightly limited mission, transparently designed to protect lives, established in response to a clear and imminent threat, which enjoyed broad international support.

That original promise is now looking decidedly shaky. The purpose of United Nations Security Council Resolution 1973 was to prevent a civilian massacre in Benghazi by forces loyal to the regime of Muammar Gaddafi. But last week David Cameron, Nicolas Sarkozy and Barack Obama jointly signed an open letter in which the three leaders came perilously close to committing themselves to a policy of full-blown regime-change in Libya.

It has already served to erode the international legitimacy of the operation. Russia has, predictably, complained that Nato has exceeded the mandate of the UN resolution. The effective sidelining of the Arab League and the African Union since the operation began has knocked off further chunks of consensus. The early hopes of military involvement from Arab states in the Libyan mission are long forgotten.

Resolution 1973 also ruled out foreign forces being deployed in Libya. But our own Government, along with that of France and Italy, is now sending a small team of "military advisers" to provide "logistics and intelligence training" to the opposition in Benghazi. The Foreign Secretary, William Hague, insists that these advisers will take no part in the fighting. Yet many will see this as a breach of the spirit, if not the letter, of the UN resolution. There are also practical problems. One of the tasks of these advisers will apparently be to help distribute aid and medical assistance. But, as Oxfam warned yesterday, to involve military personnel in the distribution of aid is to play with fire.

The temptations for Western powers to use their military resources to tilt the scales of the Libyan war decisively in favour of the rebels are great. Air strikes in recent weeks have eliminated Gaddafi's advantage, but they have not swung the war for opposition forces. Stalemate threatens. And Nato is struggling to find enough combat aircraft to maintain its air campaign. Despite much arm-twisting, Spain, Italy and the Netherlands all failed to commit their own attack aircraft at last week's meeting of the military alliance in Berlin. A quick end to the conflict would be in Western interests, particularly those nations that have taken a lead in the operation.

But Western powers need to consider the context. This is in danger of being regarded not as a struggle for self-determination by an Arab nation, but a Western-backed coup. Further, vicious repression by a dictatorial regime is also taking place in Bahrain and Syria. The absence of Western pressure on those regimes means that the toxic charge of double standards could resurface. A heavy Western hand in Libya could give a useful propaganda tool to rattled regional autocrats across the region.

The situation is fluid. There remains a risk to civilian life in Libya. The two-month siege of Misrata by Gaddafi loyalists has turned vicious. There were reports yesterday of the dictator's forces deploying cluster munitions and using heavy weaponry to fire indiscriminately on civilian areas. It would be unwise to close down options. There might yet be a case for the deployment of Nato ground troops if the threat of a massacre returns. Yet foreign powers should not be trying to force the pace of events in Libya. Whatever the temptations, this intervention will only be successful if it is guided by patient discretion, not hasty aggression.