The CIA said the probability of Iraqi President Saddam Hussein initiating an attack without provocation on the United States in the foreseeable future was "very low," according to a letter made public last night.
But if he was attacked, the likelihood that Saddam would respond with biological or chemical weapons was "pretty high."
The letter, dated October 7th, was signed by deputy CIA director Mr John McLaughlin on behalf of CIA director Mr George Tenet and sent to Senate Intelligence Committee Chairman Mr Bob Graham in response to the Florida Democrat requesting the CIA declassify parts of its secret assessment on Iraq.
The US Senate is debating how much authority to give President Bush in a war powers resolution, and some Democrats complained that the CIA was not providing intelligence that contradicted the Bush administration's views on Iraq.
The CIA assessment in the letter to Graham said Iraq appeared to have stopped short of terrorist attacks against the United States.
"Baghdad for now appears to be drawing a line short of conducting terrorist attacks with conventional or CBW (chemical and biological weapons) against the United States," the CIA said.
"Should Saddam conclude that a US-led attack could no longer be deterred, he probably would become much less constrained in adopting terrorist actions," the letter said.
"Although we think the chances of Saddam initiating a WMD (weapons of mass destruction) attack at this moment are low - in part because it would constitute an admission that he possesses WMD - there is no question that the likelihood of Saddam using WMD against the United States or our allies in the region for blackmail, deterrence, or otherwise grows as his arsenal continues to build," Mr Tenet said.
The letter declassified dialogue from a closed Senate Intelligence Committee hearing, in which a senior intelligence witness was asked what Saddam would do if he did not feel threatened.