The Government last night announced the deployment to the Gulf of a powerful amphibious task force with 3,000 Royal Marine commandos in a dramatic ratcheting up of the pressure on Saddam Hussein.

Defence Secretary Geoff Hoon said the dispatch of the force - headed by the carriers HMS Ark Royal and HMS Ocean - would leave the Iraqi dictator in no doubt that Britain "means business".

He told the Commons the deployment did not mean that war with Iraq was "inevitable", but he said it was "likely" that further forces would be sent to the region in the coming weeks.

In a further move, Mr Hoon said he was issuing mobilisation orders to hundreds of reservists - including medics, signallers and logistics experts - in the largest call out of the reserve since the 1991 Gulf War.

Initially, orders would be issued to secure about 1,500 reservists, although again Mr Hoon indicated that further call-out notices were likely to be issued in coming weeks.

A spokeswoman for the Army said it was too early to say just how many would be called up in the North-East.

They could be drawn from a number of areas including the ranks of the Territorial Army, which has about 7,800 part-time soldiers in the North-East and Yorkshire.

Hospital trusts around the region are braced for the possible call-up of their reserve medical staff.

South Tees Hospitals NHS Trust has 18 TA reserves on its books covering a wide range of staff including sisters, nurses, physiotherapists and health care assistants.

The trust's Friarage Hospital in Northallerton also has a contract with the Ministry of Defence to provide medical care to military personnel.

A spokeswoman for Darlington Memorial and Bishop Auckland hospitals said: "We have a number of doctors on our books who could be called up but have not yet had any notification of such a move."

Meanwhile, the Naval Task Group 03 will comprise 15 surface vessels and one nuclear-powered submarine with a total of 5,000 Royal Navy and Royal Marines personnel.

In a radio interview following his Commons statement, Mr Hoon appeared to demonstrate his irritation with comments by Foreign Secretary Jack Straw suggesting the chances of war had slipped to 60-40 against.

"I don't believe that it helps to make those kind of comments at this stage," he told BBC Radio 4.

Tony Blair, meanwhile, underlined his determination to stand shoulder-to-shoulder with US President George Bush as America's "closest ally" in the current crisis over Iraq.

He said that if Britain wanted to influence the US over issues such as climate change, Third World poverty or the Middle East, it had to back America when it came to dealing with weapons of mass destruction or terrorism.

"I would never commit British troops to a war I thought was wrong or unnecessary. But the price of influence is that we do not leave the US to face the tricky issues alone," he told a conference of British ambassadors in London