British Army officers are being sent to Libya to advise rebels fighting Colonel Muammar Gaddafi's forces.
The UK group will be deployed to the opposition stronghold of Benghazi, Libya's second city, in a mentoring role to help leaders co-ordinating attacks on the dictator's army.
The announcement came after a Royal Navy submarine launched cruise missiles on Libyan targets, with RAF warplanes attacking communication masts.
The handful of experienced officers will join a British team in Benghazi working with the opposition National Transitional Council (NTC), which UK Foreign Secretary William Hague described as "legitimate political interlocutors".
Mr Hague said the Army officers would help prevent attacks on civilians, in line with the United Nations Security Council resolution authorising military action against Gaddafi's forces.
He said: "These additional personnel will enable the UK to build on the work already being undertaken to support and advise the NTC on how to better protect civilians.
"In particular they will advise the NTC on how to improve their military organisational structures, communications and logistics, including how best to distribute humanitarian aid and deliver medical assistance."
The Foreign Secretary added: "Our officers will not be involved in training or arming the opposition's fighting forces. Nor will they be involved in the planning or execution of the NTC's military operations or in the provision of any other form of operational military advice."
Britain has supplied rebels with body armour and telecommunications equipment and the Government on Monday pledged £2 million to help thousands of stranded civilians flee war-torn Misrata by boat.
Speaking later to Sky News, Mr Hague again ruled out a ground invasion to unseat Gaddafi, but admitted further SAS raids were possible for specific missions.