There were grim predictions yesterday of a lengthy conflict if the US launches an all-out revenge attack for the terrorist outrages.

Officials vowed to eradicate the terror group which hit New York and Washington, killing thousands, and said they would also retaliate against the states which supported them.

And the Prime Minister told an emergency session of Parliament that Britain would join the US in hunting down those responsible for the "hideous and foul" attacks.

He said the murder of at least 100 Britons caught up in the strikes should be treated as if they were killed "in the heart of Britain itself".

Mr Blair said action "will be determined, it will take time, it will continue over time until this menace is properly dealt with and its machinery of terror destroyed".

Others called for caution, warning that a heavy-handed strike risked creating a new generation of terrorists and conflict with the Islamic world.

Former Liberal Democrat leader Lord Ashdown even warned of the potential for nuclear war if the US was to alienate some Islamic states.

And the Taliban regime in Afghanistan threatened "revenge" if the US attacked it for harbouring chief suspect Osama bin Laden.

Nato chief Lord Robertson declared that the alliance would not lash out blindly in revenge for the terrorist attacks.

Describing the carnage as "an attack on all of us, on our values, on our open societies", Lord Robertson pledged that the 19 countries of the alliance would not stoop to the level of the terrorists.

"The mad creatures who committed these terrible crimes this week may have hoped to provoke us into mindless revenge in order to create even more devastation," he said. "They are wrong."

But veteran Labour MP Tam Dalyell, Father of the House as the longest serving MP, urged Britain not to kill innocent civilians in revenge attacks.

"If we do so, we simply recruit more terrorists," he said.

Labour Left-winger Dennis Skinner was more outspoken, bringing cries of "shame" from fellow MPs when he said there was "a world of difference" between standing shoulder to shoulder with the American people and "clinging to the coat tails of an American President . . . whose first act when those firefighters were standing ten feet tall among the rubble of the World Trade Centre was to scurry off to his bunker".

And European leaders sought to quell any moves toward war-mongering in the wake of the terrorist attacks, with several figures saying that "we are not at war".

French Prime Minister Lionel Jospin, after leading his Cabinet in the Europe-wide three-minute silent commemoration for victims, reiterated the need for an "implacable and long fight against terrorism."

But he also said: "We are not at war against Islam or the Arab-Muslim world."

Hours earlier, Belgian foreign minister Louis Michel, said that the EU was "on watch" and "mobilised," but added: "We are not at war."

In the US, police swooped on Thursday night at two New York airports on several men reported to be armed with knives and fake pilot identification.

But Senator Joseph Biden, a member of the Senate's intelligence committee, said yesterday that none of the men were terrorists attempting a repeat of Tuesday's hijackings. "One was actually a pilot," he said.

In Minnesota, the possibility emerged that the FBI knew before Tuesday's attack of at least one Arab man seeking the type of flight training the hijackers received.

US officials confirmed that a few weeks ago the FBI detained an Arab man in Minnesota when he tried to seek flight simulator training for a large jetliner. Those who hijacked the four airliners received similar training.

The FBI released the names used by the 18 men it believes were the hijackers, amid claims US intelligence was warned last June of a terrorist "spectacular" on the country.

Intelligence officials are thought to have had "an inkling" about an attack, but details were too vague at the time to indicate the scale of the horror which unfolded on Tuesday morning