A CIA spokesman declined to comment. 

The New York Times first reported the information Saturday on its Web site. 

The counterterrorism officials said operatives may be planning to use explosives or toxins to conduct the attack. 

The new information comes against a murky backdrop regarding whether Iraq supports al-Qaida, or to what extent there are ties. 

However, intelligence officials have generally agreed they have nothing to document that Saddam Hussein had a hand in the Sept. 11, 2001, attacks or that Saddam and Osama bin Laden are coordinating terrorist operations. 

At the center of U.S. allegations that there are links between Iraq and the terrorist group is Zarqawi, a Jordanian terrorist operative, and some of his followers. 

CIA Director George Tenet and others have described Zarqawi as a senior associate of al-Qaida leader Osama bin Laden, but officials acknowledge some difference of opinion within U.S. intelligence whether it is correct to describe him as a member of the organization. 

Zarqawi has been linked to the failed millennium bombing of a tourist hotel in Jordan and the killing of an American diplomat in Amman in October. 

According to U.S. officials, Zarqawi was in Baghdad last summer, presumably with the knowledge of Iraqi officials. Some of his people are still there. Zarqawi is also linked to an Islamic extremist group in northern Iraq, Ansar al-Islam, that operates in a region outside of Saddam's control. 

An agent from Iraq's government is working for Ansar, Secretary of State Colin Powell said in a Feb. 5 presentation to the U.N. Security Council. Powell said this agent had offered safe haven to some al-Qaida operatives in the region. 

But Powell omitted an important point: U.S. officials later acknowledged they don't know what this Iraqi operative is doing with Ansar al-Islam, and they do not know whether Ansar is aware he works for the Iraqi government. 

While the agent could be openly representing Saddam's government, he also could be spying on the group for Saddam's security services, officials said. 

According to intelligence officials, Zarqawi believes he is operating independently of al-Qaida's chain of command. But they say while he manages his own network of followers, he relies on al-Qaida money and logistical support, making him - in effect if not in reality - a lieutenant of bin Laden. 

What is known, according to Powell, Tenet and other officials: 

Zarqawi was around Herat in western Afghanistan in October 2001, when the U.S. attacked the Taliban and their al-Qaida allies. He ran a camp in the region that experimented with poisons and chemical weapons. 

Officials say he may have been wounded in the leg, probably by U.S. bombing. He crossed the border into Iran, where he reportedly received some medical treatment. U.S. intelligence learned of his presence there, prompting Defense Secretary Donald Rumsfeld in April 2002 to accuse Iran of sheltering al-Qaida terrorists. 

The following month, Zarqawi went to Baghdad. The reasons for his departure from Iran are unclear, but he received more medical treatment in Baghdad, possibly being fitted with a prosthetic leg, and stayed there two months. 

While he was in Baghdad, about two dozen of his followers moved to the city. Some are still there, including two senior members of Egyptian Islamic Jihad, a terrorist network that merged with al-Qaida during the last few years. 

U.S. officials say Saddam's security apparatus is too effective for them not to know Zarqawi and his followers were in town. But no officials claimed evidence that Zarqawi and the Iraqis are actively working together to conduct terrorist attacks. 

U.S. intelligence learned of Zarqawi's presence in Baghdad while he was there, and a friendly foreign government twice asked Baghdad about him and was rebuffed both times. Zarqawi left shortly after the inquiries. 

Iraqi Foreign Minister Naji Sabri said Baghdad had no ties to Ansar al-Islam, nor to an alleged al-Qaida fugitive Abu Musab Zarqawi. 

In July, shortly after the foreign government's inquiries, Zarqawi left Baghdad. U.S. defense officials said he was later reported in Syria. Officials suspect he also went to northern Iraq where Saddam holds little authority. 

In that region, his followers, working with Kurdish members of Ansar al-Islam, established a new camp to research poisons and make explosives. They trained others in the production of ricin, a poison that can be used as a biological weapon. 

Their ties were widespread, spanning the countries of Georgia, France, Spain, Great Britain, Russia and possibly Italy. 

European authorities have arrested 116 members of Zarqawi's extended network, including members of a British cell that was believed to be making ricin in a London apartment. 

Zarqawi's whereabouts are unknown. 

His time in Baghdad is not the only link claimed by U.S. officials. Others include: 

-An al-Qaida source said Saddam and bin Laden agreed not to oppose each other in the mid-1990s. 

-Senior representatives of both organizations met at least eight times since the early 1990s. This includes a trip by Iraq's ambassador to Turkey to Afghanistan in 1998. 

-An Iraqi intelligence operative turned defector said Saddam sent agents to Afghanistan to provide training to al-Qaida in document forgery. 

-An al-Qaida training camp commander from Afghanistan, now in U.S. custody, said al-Qaida sought chemical and biological weapons training from Iraq between 1997 and 2000. One operative later characterized his efforts in Iraq as successful.