Members of the SAS are poised to join US, French and Italian counterparts in targeting the Libyan city of Sirte, thought to contain 5,000 followers of the fanatical death cult.
The move is part of a wider effort to squeeze IS in both Libya and Iraq.
Defence Secretary Michael Fallon confirmed that the deployment of patrol ship Enterprise would be extended off the coast of Tripoli, where its electronic warfare team is gathering vital intelligence.
Other sources added that another naval support vessel will be positioned off the coast of Sirte, ready to intercept any ships carrying Islamic extremists or weapons.
Their job will be to ensure that IS forces do not use human shields, as they anticipate the air onslaught to come.
American B52 bombers, famed for their carpet-bombing in Vietnam, were last night awaiting orders to deploy from their base in Qatar. The “stratofortress” behemoth is able to drop precision-guided bombs and can destroy as many as 50 targets in one mission.
Now both Iraqi and Kurdish forces are going through final training and being issued with additional equipment, including chemical warfare suits, in readiness for a major ground assault led by 70,000 Arab troops.
The retaking of Mosul – expected to happen “within a fortnight” – will leave increasingly beleaguered IS forces with just a single stronghold: the Iraq city of Raqqa.
British Special Forces are already inside Libya, working as “advisers” within a joint special operations force which has been tracking IS fighters for the past month using drones and surveillance spy planes operating out of Cyprus.
A senior military source said: “Our people have been on the ground in Libya for some weeks, albeit in an advisory role, but the mission has now changed.
“They are under US command as part of a Joint Special Operations Force and their mission is to target enemy forces in a series of precision strikes so that Sirte can be liberated by Libyan army personnel.”
Specialist teams have also been training on the Italian island of Pantelleria, just 37 miles off the Tunisian coast, as well as at a UK military base in Tunisia.
According to senior military sources, Obama and Cameron have discussed concerns by US intelligence forces that IS forces have been supplied with Chinese-made anti-tank missile launchers by militants in Sudan.
A coalition force, including 1,000 British troops, is on standby to “support the stabilisation operation” after the IS threat has been eliminated.
The battle group, led by a British brigadier, is soon to be deployed to Tripoli.
Though it will include paratroopers acting in a force protection role, the bulk of the troops will occupy themselves with technical duties, such as clearing roadside bombs.
express.co.uk
