Turning up the political heat on Iraq, the Bush administration said Thursday that Baghdad is so completely in cahoots with Al Qaeda that it has harbored top aides to Usama bin Laden and may have trained the terrorists in germ and gas warfare.

Defense Secretary Donald H. Rumsfeld said the United States has evidence that senior members of Al Qaeda have been in Baghdad "in recent periods," but they did not include bin Laden. It's unclear whether they remain in the Iraqi capital, he said, because they are "moving targets."

Rumsfeld said he had high confidence in this information, but he acknowledged that the intelligence reporting is based on different types of sources of "varying degrees of reliability." He said some of the information came from suspected Al Qaeda members in U.S. detention.

Iraq denies it supports Al Qaeda.

"We have what we believe to be credible information that Iraq and Al Qaeda have discussed safe haven opportunities in Iraq [and] reciprocal nonaggression discussions," Rumsfeld told a Pentagon news conference.

He cited "solid evidence" of Al Qaeda members in Baghdad, but at one point he refrained from explicitly stating they had received a government-sanctioned grant of safe haven. That, he said, "happens to be a piece of intelligence that either we don't have or we don't want to talk about."

Just a day earlier, when asked during a news conference in Poland about alleged links between Al Qaeda and Iraq, Rumsfeld would say nothing except to assert that such links exist. He said Thursday that he was at liberty to elaborate because some intelligence had been declassified.

Other senior administration officials joined in throwing accusations at Iraq that appeared designed to bolster President Bush's argument that Iraq poses such a grave danger that Saddam Hussein must be deposed, by force if necessary.

"Al Qaeda and Iraq are too close for comfort," White House press secretary Ari Fleischer said.

Secretary of State Colin Powell told the Senate Foreign Relations Committee that "there is evidence of a linkage" between Iraq and Al Qaeda. He said he was unaware of any Iraqi link to the Sept. 11 terror attacks but would not dismiss the possibility.

Rumsfeld and the Pentagon's top military officers met at the White House with Bush to discuss a range of issues including Iraq. The officers included the chiefs of the Army, Navy, Air Force and Marines as well as the chairman and vice chairman of the Joint Chiefs of Staff.

Thursday's statements, which echoed those made previously by national security adviser Condoleezza Rice, are the strongest yet alleging Iraqi complicity with Al Qaeda. Previously, evidence of the two working together was tenuous, or came from what U.S. officials called unreliable sources.

Rumsfeld said "senior level contacts" between Al Qaeda and Iraq go back a decade and have been increasing since 1998. In that year the Iraqi ambassador to Turkey traveled to Afghanistan to meet with senior Al Qaeda leaders, another U.S. official said, speaking on condition of anonymity.

The administration has been less specific about information pointing to Iraqi assistance to Al Qaeda on chemical and biological weapons. Rice said in an interview with PBS' The NewsHour with Jim Lehrer on Wednesday that several Al Qaeda detainees have said that Iraq provided "some training to Al Qaeda in chemical weapons development."

Rumsfeld made the same assertion in a more qualified way.

"We do have, I believe it's one report indicating that Iraq provided unspecified training relating to chemical and/or biological matters for Al Qaeda members." He added that there is other information "of varying degrees of reliability" that supports that single report.

In a carefully worded statement, Rumsfeld also asserted that the U.S. government has credible evidence that Al Qaeda leaders have "sought contacts in Iraq" who could help them acquire weapons of mass destruction capabilities. He did not say whether Iraqis provided such help.

The widely held view has been that while Saddam and bin Laden both oppose the United States, their motivations are too different for them to work together. Saddam seeks secular power; bin Laden's drive comes from religious motivations and his opposition to the U.S. military presence in Saudi Arabia and the Arab world.

"No one is trying to make an argument at this point that Saddam Hussein somehow had operational control of what happened on Sept. 11, so we don't want to push this too far, but this is a story that is unfolding, and it is getting clearer, and we're learning more," Rice said.

Previously, U.S. intelligence officials have said some Al Qaeda members have been detected in Iraq, but that they appeared to simply be crossing the country while fleeing Afghanistan.