B-52s flown from Fairford launched the Kosovo war

The long-range bomber - thought likely to be involved in any conflict in Iraq - is the first of up to 14 expected to be arriving at RAF Fairford.

Meanwhile, Tony Blair is stepping up his diplomatic campaign seeking support for a second UN resolution on Iraq, with phone calls and meetings with world leaders.

In Iraq, British and American pilots patrolling the no-fly zones have begun targeting Iraqi weapons that might be used in a war.

B-52 Stratofortress Wingspan: 56m (185ft) Range: 12,870 km (8,000 miles) Bomb load: 4,536kg (10,000lb) Click here for full factfile

Mr Blair spoke to the prime ministers of the Netherlands, Denmark and Chile over the weekend.

He will talk to other world leaders ahead of chief weapons inspector Hans Blix's next report on Friday, and meets Russia's foreign minister in London on Tuesday.

Mr Blair believes Saddam Hussein hopes to weaken the UN's will with last-minute concessions over missiles.

Iraq has begun destroying al-Samoud II missiles banned since the Gulf War, but threatens to stop if the US continues to pursue war without UN backing.

Resolution 1441 means what it says Tony Blair's spokesman

"Given the history of deception, cheating and lies it is understandable we should be approaching what we are seeing with a degree of scepticism," said the prime minister's official spokesman.

"At the very last moment he puts out concessions to weaken the resolve of the UN. He wanted to turn the missiles issue into the issue against which his co-operation should be judged."

Saddam had refused to answer outstanding questions over chemical and biological weapons, the spokesman said.

"Resolution 1441 means what it says. He has to disarm or prove to the satisfaction of the UN that he has disarmed."

Stealth bombers

Fairford is a NATO-designated standby base shared with the United States Air Force.

One of only three forward USAF bases outside the USA, it was involved in the Kosovo conflict - Fairford-based bombers carried almost half the bombs dropped during that war.

The base can also now house B-2 Stealth bombers - doubling its potential strike force - since a �100m refurbishment in 2002.

The USAF's role at the base is sensitive and Fairford has recently been the focus of anti-war protests.

The US military is taking advantage of the no-fly zones to prepare the battle space for war Defence analyst Loren Thompson Gulf states say Saddam should go - Click here

B-52s flown from Fairford four years ago began Nato's assault on Yugoslavia, which ultimately led to Serbian forces being ejected from Kosovo.

American B-52s also flew 60 missions during the first Gulf conflict, dropping more than 1,158 tonnes of high-explosive on key targets in Iraq and Kuwait.

The aircraft can carry a variety of bombs and other weapons, including Tomahawk cruise missiles.

The Ministry of Defence says it cannot comment on the movement of US aircraft and has not officially confirmed B-52s will be stationed at Fairford.

Meanwhile US media reports suggest some American forces might be put under British command in the event of war.

The Washington Post quotes US officials in Kuwait as saying the American 15th Marine Expeditionary Unit is likely to be assigned to a British command in the event of war.

The move, unseen since Montgomery commanded American troops in World War II, is said to be a gesture rewarding Tony Blair for his support.

'Reckless beyond belief'

A London think-tank has also warned the US may lose interest in Iraq after a possible war, leaving the same power structure in place.

The Royal Institute of International Affairs said even a swift victory over Baghdad would be no guarantee of real US commitment to Iraqi political reforms.

The paper estimates tackling Iraq's structural and political problems will take three to 10 years, but believes fears over cost and casualties may make the US reluctant to get involved for that long.

Report author Toby Dodge said it was "reckless beyond belief" to have no coherent post-conflict plan.

The report also warned of likely regional knock-on effects, including economic misery, a rise in Islamic fundamentalism and huge refugee flows.

Two no-fly zones banning Iraqi aircraft flights over part of the country were imposed after the Gulf War as part of the US policy of containing Saddam Hussein.

The MoD says it is still the public position that US and British patrols should only attack in self-defence.

But Iraqis claim western planes are hitting civilian targets.