The Pentagon was reported yesterday to be considering a daring new war plan to oust Saddam Hussein, by unleashing a surprise direct assault on Baghdad and other key command centres with the aim of decapitating the regime in a few days.

The "inside-out" plan, reversing the tactics used in the Gulf war by striking at the heart of the regime first, is the latest in a series to be leaked to the press in recent weeks amid a very public build-up of administration rhetoric and flexing of Pentagon muscles.

Observers differed over whether the leaks reflected strategic disagreements in Washington or a deliberate propaganda campaign aimed at intimidating and confusing Baghdad.

The plan, as described in the New York Times, would fly US troops into Baghdad on the first day of the campaign, delivering a powerful shock to the Saddam regime and to the Iraqi people, convincing them in one bold stroke that the US was determined to topple the dictator. The inside-out approach would also be aimed at killing Saddam Hussein or at least isolating him before he could unleash any working biological or chemical weapons in his arsenal. It would also avoid massing large numbers of US troops along Iraq's borders where they could be vulnerable to weapons of mass destruction.

"There is a divergence of views on how can one best diminish the prospect that he uses weapons of mass destruction, with any efficacy," Joseph Biden, the chairman of the Senate foreign relations committee, said. "That is where the argument for an inside-out operation gains credibility. There is a diminished possibility that he will use chemical or biological weapons."

However, the plan could well involve American soldiers fighting their way through the streets of Baghdad and other cities against Iraq's best and most determined troops, the special republican guard, instead of pushing towards the capital in the hope that the regime would implode before US forces reached the outskirts of the city.

The debate on how to get rid of Saddam has been under way in earnest since January when the Bush administration decided to pursue a policy of "regime change' in Iraq. The first plan put forward was a variant of OPLAN 1003, which US central command had had on its shelves since the Gulf war 11 years earlier. It involved 250,000 troops and a build-up of three months.

The central command plan was quickly criticised by civilian strategists at the Pentagon as too lumbering and old-fashioned for a new era of advanced technology and highly mobile forces. They argued that the job could be done much faster with as few as 50,000 troops which could be inserted into the region quietly over a few weeks, allowing the US to launch a surprise attack from Kuwait, Qatar and other Gulf bases.

The OPLAN 1003 variant was leaked to the press earlier this month, apparently by radical thinkers at the Pentagon who were frustrated by the lack of creativity behind it. Some analysts said yesterday that the new inside-out plan could have been leaked in order to counter suggestions by apprehensive US officers that an attack on Iraq was too huge and risky an undertaking compared to the current policy of containment.

John Pike, the head of GlobalSecurity.org, a military and intelligence thinktank, suggested there was an element of disinformation behind the leaks, aimed at catching the Baghdad regime off guard.

"One element of the operation if I were planning it would be strategic deception as to the plan and the timing," Mr Pike said. "If I wanted 50,000 men to march on Baghdad, I would certainly do everything in my power to give the impression that I was going to wait months while I put together a force of a quarter million."

Michael O'Hanlon, a defence expert at the Brookings Institution in Washington, argued there was nothing new in the inside-out approach. He said any feasible attack plan would involve a surprise assault on the core of Saddam's power, at the same time as air and ground assaults elsewhere.

He also pointed out that yesterday's New York Times report conceded that the plan would probably require a force of "something nearer the 250,000 figure" to ensure that the initial strike force was not stranded inside Iraq.