The US Central Intelligence Agency (CIA) believes Iraqi leader Saddam Hussein could respond with chemical or biological weapons if he thinks an American-led strike against him is imminent.

For now (Saddam Hussein) appears to be drawing a line short of conducting terrorist attacks with conventional or chemical weapons

George Tenet, CIA director

But in a letter to the Senate Intelligence Committee, CIA director George Tenet also said the likelihood of Iraq launching an unprovoked attack on the United States was "low".

In a subsequent statement, Mr Tenet insisted that the letter did not contradict President Bush's tough stance on Iraq.

It comes as Congress is debating a resolution authorising President Bush to use military force against Baghdad.

Mixed signals

According to Mr Tenet's letter, Iraqi leader Saddam Hussein might help Islamic militants use weapons of mass destruction against the US if he sees it as "his last chance to exact vengeance".

For now, the letter says, Baghdad "appears to be drawing a line short of conducting terrorist attacks with conventional or chemical weapons".

Saddam is said to have deadly weapons as well

But should Saddam Hussein conclude that a US-led attack could not be deterred, "he probably would become much less constrained in adoption terrorist action," the letter said.

The BBC's Roger Hardy says the letter provides ammunition for both supporters and opponents of the Bush administration's policy.

On the one hand, he says, it seems to suggest that an attack on Iraq would be likely to provoke the one thing Mr Bush says he is trying to prevent - the use of chemical or biological weapons by Saddam Hussein.

The letter was mailed on Monday - the day President Bush delivered a speech making the case for the possible use of force to disarm Iraq, warning that waiting was "the riskiest of all options".

But at the same time, the letter backs up the President's assertion that there have been high-level contacts between Iraq and al-Qaeda for a decade.

"We have solid reporting of senior-level contacts between Iraq and al-Qaeda going back a decade," Mr Tenet wrote.

"Credible information" also indicates that Iraq and al Qaeda "have discussed safe haven and reciprocal non-aggression," he added.

'Growing arsenal'

CIA director George Tenet, for his part, insists there is "no inconsistency" between his letter and the president's policy.

Some at CIA may be uneasy about the war effort

In a statement released on Tuesday, he said Baghdad's links to Islamic militants was likely to increase even absent US military action.

"There is no question that the likelihood of Saddam using weapons of mass destruction against the United States or our allies grows as his arsenal continues to build," he said in the statement.

However correspondents say some CIA officials are concerned that the agency - whose role is to give politically neutral information to the President - may be endorsing the administration's agenda.

Mr Tenet's assessment comes as both the House of Representatives and the Senate are debating a congressional resolution to authorise President Bush to use force against Iraq.

The resolution in expected to be approved next week.