Washington ? In growing detail, Bush administration officials are presenting their case that Iraq retains a hidden and fearsome arsenal of nerve gases, blister-producing chemicals, anthrax and other lethal agents.

They say Saddam Hussein has built mobile killer germ laboratories and may be scouring Africa for uranium to construct a nuclear bomb. They add that thousands of Iraqi “anti-inspectors” are thwarting U.N. weapons monitors, burying weapons and documents in lakes, under mosques and on farms.

Even as a “smoking gun” eludes U.N. inspectors, and the Bush administration inches toward an invasion of Iraq, a growing number of experts accept that Saddam has been deceiving the world about his arsenal.

In contrast, opinion polls show that many Americans are still deeply wary of going to war against Iraq. Some say the administration is banging the war drum without providing sufficient proof that Saddam should be toppled now. Others flatly disbelieve administration charges alleging hidden Iraqi munitions.

Seeking to address those concerns, the Bush administration and the British government of Prime Minister Tony Blair have offered a series of public assessments in recent days that Iraq is hiding stockpiles of banned weaponry, flouting United Nations demands that it disarm.

Deputy Secretary of Defense Paul Wolfowitz said Thursday that Iraq had enough concentrated biological agents “to kill hundreds of millions” of people.

Wolfowitz dismissed the argument that the Bush administration should give U.N. weapons inspectors significantly more time to uncover Saddam’s hidden arsenals. The U.N. inspections chief, Hans Blix, will issue a report on the team’s work on Monday.

“It is not the job of inspectors to disarm Iraq,” Wolfowitz said at the Council on Foreign Relations in New York. “It is Iraq’s job to disarm itself.”

Wolfowitz added: “It is quite unreasonable to expect a few hundred inspectors to search every potential hiding place in a country the size of France, even if nothing were being moved.”

An eight-page White House report on Thursday said Iraq “has chosen to conceal and to lie” about its weapons to U.N. inspectors rather than to cooperate.

Administration officials have seized on the discovery by U.N. weapons inspectors in Iraq last week of at least 12 empty warheads capable of carrying chemical payloads.

If empty Iraqi warheads were filled with sarin, a deadly nerve agent used by Japanese terrorists in 1995 that killed 12 Tokyo subway passengers and sickened thousands, “it would contain over 40,000 lethal doses,” the White House report said.

Among the most unsettling public assertions of the Bush administration this week is that Saddam’s regime has never accounted for 1.5 tons of a nerve gas known as VX. The lethal nerve agent causes acute muscular spasms and paralysis.

“This is an incredibly lethal toxin. If a microscopic amount touches your skin, it will quickly kill you,” said Jon Wolfsthal, deputy director of the nonproliferation project at the Carnegie Endowment for International Peace in Washington.

The White House report said that if Iraq put VX gas in a warhead of a type that it is known to have manufactured, then launched it at a major city, it could kill up to 1 million people.