Government officials said the research mimicked major steps a state or terrorist might take to create a biological arsenal and was intended to understand the threat better.

Without an aggressive inspections program, Mr. Ritter testified, Iraq could rebuild its nuclear, chemical and biological arsenals in six months.

Government officials said the secret research, which mimicked the major steps a state or terrorist would take to create a biological arsenal, was aimed at better understanding the threat.

The Iraqis claimed to have destroyed their biological arsenal immediately after the 1991 war, but they did not provide confirmatory evidence.

For the moment, diplomacy has defused the latest standoff over allowing United Nations inspectors to resume their hunt for Iraq's nuclear, chemical and biological arsenal.

As to building a biological arsenal from imported vaccines, "the answer is no," said Alan Goldhammer of the Industrial Biotechnology Association, a trade group.

CAN Iraq really hide a nuclear, biological or chemical arsenal, however skillfully it can run and duck?

With a possible biological arsenal present?

There are no hard numbers on the exact size of Iraq's chemical or biological arsenal before the war.

Since the 1991 cease-fire, U.N. inspectors have largely disarmed Saddam's nuclear, chemical, and biological arsenal, using random inspections and surveillance cameras to do their work.