The proposal, which will fuel tensions between Washington and Damascus, was condemned by British military officers as a breach of international law that would add to regional instability.

British and US intelligence agencies are uncertain whether Saddam is even alive, let alone where he is.

A senior US source at Central Command said that although troops hunting members of the Iraqi regime were under orders to respect Syria’s borders, an exception would be made for Saddam.

American special forces in western Iraq have been told that they can enter Syria to grab the former President, and in all likelihood kill him, if they have “credible Intelligence” of his whereabouts. Their commanders would justify the action under the doctrine of “hot pursuit”, the disputed theory that soldiers who are in the act of hunting a terrorist suspect are allowed under international law to enter a foreign country without permission.

The suspect’s alleged crimes need to be sufficiently serious to justify the violation of the country’s territorial integrity. The source suggested that the action would be taken even if it could not be justified legally.

“We respect international law,” he said. “But if it was the ace of spades, it would be different.” American soldiers in Iraq have been given a deck of cards showing the faces of 55 fugitive leaders of the regime: Saddam is the ace in the pack.

British officers, publicly at least, are opposed to the plans.

“By the very nature (of international law) you should not go crossing international borders in an illegal manner,” a British military spokesman said.

The plan was revealed amid reports from Washington that Farouk Hijazi, the former head of the overseas arm of the Mukhabarat, Saddam’s secret police, had flown to Damascus. Mr Hijazi, Saddam’s Ambassador to Tunisia, is suspected of playing a key role in the plot to assassinate President Bush Sr when he visited Kuwait in 1993.

Like other second-string members of the regime, a bounty of about £140,000 has been placed on his head. The prize for turning in Saddam is said to run into several millions of pounds.

An operation by special forces would prevent protracted diplomatic wrangling with the Syrians over his fate.

Washington accused Syria last week of harbouring members of Saddam’s regime, but Brigadier-General Vincent Brooks told Centcom’s daily briefing in Qatar yesterday: “There has been a sharp fall in the numbers of people moving between Syria and Iraq . . . The action of special forces in the border areas and top-level diplomatic discussions have had an impact.

He added: “If we don’t find every leader, but the regime is no more, then we will still have succeeded.”

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