Iraqi efforts to thwart weapons inspections date back to when they began in 1991, former inspectors say.

Secretary of State Colin Powell's presentation Wednesday to the U.N. Security Council included what Powell said was evidence Iraq was trying to hide banned weapons from inspectors in recent months. Former inspectors say Iraq did the same thing during the 1990s -- moving weapons or documents from sites before inspectors arrived, for example.

"It appears that Iraq's deception and denial system was reconstituted when it became clear that inspectors were returning," said former inspector Jonathan Tucker. "Iraq didn't change its stripes."

Tucker and other former inspectors said Powell's presentation disclosed intelligence on Iraq's banned weapons programs in unprecedented detail. For example, Powell played recordings he said were intercepted transmissions between Iraqi Republican Guard officers.

Part of the reason Powell chose the Republican Guard tapes could be that Iraqis already knew such transmissions were not secure, said former inspector Timothy McCarthy.

McCarthy, a missile expert, said he was struck by Powell's assertion that Iraq moved rockets loaded with biological agents from the Baghdad area to western Iraq a few months ago. Iraq has unguided rockets with ranges from about 12 miles up to about 110 miles, McCarthy said.

Some of the satellite pictures Powell showed seemed as detailed as the images former inspectors got from the U-2 surveillance planes Iraq is now blocking, said Raymond Zilinskas, another former inspector.

"If the Iraqis think a facility is about to be inspected, they bring in the trucks to move equipment or weapons or documents. That can be picked up by a U-2," said Zilinskas, now with the Center for Nonproliferation Studies at the Monterey Institute for International Studies in California.

U-2 planes are important not only because of the highly detailed pictures they can take but also for their other capabilities, such as heat sensors that can detect activity at underground weapons sites, Zilinskas said.

Chief U.N. inspector Hans Blix has repeatedly pressed Iraq to allow U.N.-sponsored U-2 flights and says he will bring up the issue again when he meets with Iraqi officials in Baghdad this weekend. Iraq has balked, insisting it can't guarantee the surveillance planes' safety as long as the United States and Britain continue to patrol no-fly zones over northern and southern Iraq.

Such resistance is surprising, given the fact that the United States is building up its military forces in the region in preparation for possible war, said former inspector Jonathan Tucker.

"It's difficult to understand the Iraqi mentality. They basically put a gun to their own head," said Tucker, a visiting fellow with the U.S. Institute for Peace in Washington.

Powell also said the United States had detected a test flight of an Iraqi "unmanned aerial vehicle" -- a remote-controlled plane -- of about 310 miles. Those drones would be ideal for spreading biological or chemical weapons, Powell said.

McCarthy said the drone Powell discussed apparently had never been revealed before. However, flying for 300 miles in a loop over Iraq is much easier than flying 300 miles in a straight line, McCarthy said.

"In a point-to-point flight, it may not be steerable beyond the tracking range of its radar," McCarthy said.

He and other former inspectors said Powell made a strong case at the United Nations.

"It's hard not to be convinced by this evidence," said Terence Taylor, a former top U.N. inspector.

Convincing reluctant members of the Security Council to approve a war against Iraq may have been all but impossible, however, McCarthy said.

"Unless you had a picture of Saddam Hussein standing next to a nuclear weapon, I doubt you would have changed any minds," he said.