Washington ? Defense Secretary Donald H. Rumsfeld said Wednesday he still thought Iraq may have had weapons of mass destruction before U.S. troops invaded, the Bush administration’s hardest push-back against a weapons inspector’s assertions that stockpiles did not exist.

President Bush and his aides have in recent days backed away from their often-stated predictions that such weapons would be found.

But in a sometimes contentious hearing before the Senate Armed Services Committee, Rumsfeld still held out the possibility and denied assertions by Democrats that Bush administration officials manipulated intelligence to push for war.

Ten months into the weapons hunt, Rumsfeld said U.S. inspectors need more time to make conclusions about whether chemical and biological weapons existed in Iraq before the invasion.

Rumsfeld offered examples of what he called “alternative views” on why no weapons have been discovered, starting with the possibility that banned arms never existed.

“I suppose that’s possible, but not likely,” he said.

Other possibilities Rumsfeld cited:

• Weapons may have been dispersed throughout Iraq and hidden.
• Weapons may have been transferred to a third country before the March invasion.
• Weapons existed but were destroyed by Iraqis before the war started.

Or “small quantities” of chemical or biological agents may have existed, along with a “surge capability” that would allow Iraq to rapidly build an arsenal of banned weapons, Rumsfeld said. Commenting on that possibility, Rumsfeld said, “We may eventually find it in the months ahead.”

He also offered the possibility that Saddam was “tricked” by his own people into believing he had banned weapons that did not exist.

President Bush is planning an independent investigation to examine whether U.S. intelligence on Iraq was wrong and why.

Bush agreed to the investigation this week partly to calm a storm created days before by former head weapons inspector David Kay, who said that intelligence officials and other experts “were almost all wrong” about Saddam’s alleged programs.

Sen. Edward Kennedy, D-Mass., told Rumsfeld that Kay’s conclusion was “a devastating refutation of the Bush administration’s case for war in Iraq” that “seriously undermines our credibility in the world.”