United Nations ? U.N. weapons inspectors, who today will lay down demands to Iraq about getting back into the country, may not get the unfettered access demanded by the United States unless the Security Council alters a deal made in 1998.

The inspectors are dusting off old equipment, ordering helicopters and testing new technology as the United States negotiates a new proposal for their return.

The Bush administration dismissed Iraq’s offer earlier this month to accept the inspectors’ unconditional return under previous U.N. resolutions. Instead, it wants a tough new resolution completely redesigning the inspections regime and the powers inspectors would have to enter Saddam Hussein’s palaces, block his movements and break in on closed facilities during their hunt for weapons.

“This resolution that we’re working on has to give the inspectors all the access they need, and there cannot be any conditions on presidential sites or sensitive sites, that just can’t happen,” one U.S. official said.

Hans Blix, the chief U.N. weapons inspector, and Jacques Baute, the head of the International Atomic Energy Agency’s nuclear team, today begin two days of talks with Iraqi experts in Vienna, Austria, to arrange for the inspectors’ return.

The Iraqis are supposed to bring a backlog of reports listing items they possess which could have military purposes. The lists must disclose the locations and current uses for those items.

“We’re certainly aware of what happened last time,” said Melissa Fleming, spokeswoman for the Vienna-based IAEA. “But we uncovered Iraq’s secret nuclear program and we dismantled it. If we get unfettered access, we will be successful again.”

Although they have not been inside Iraq since December 1998, international inspectors are certain Iraq has a biological weapons program.

Some experts also believe that, despite 12 years of sanctions in place since Iraq invaded Kuwait and lobbed Scud missiles at Israel and Saudi Arabia, Saddam is ready to build a nuclear bomb if he gets enough weapons-grade uranium or plutonium.

Britain said last week that Iraq had a growing arsenal of chemical and biological weapons capable of being launched within 45 minutes. Washington also has claimed Iraq had ties to Osama bin Laden’s al-Qaida terror network.

But unless they are on the ground, inspectors say there is no way to know just how quickly Iraq is resuscitating its programs.

When U.N. inspectors first arrived in Baghdad in the aftermath of the 1991 Persian Gulf War, they were a powerful, almost untouchable force. Operating like commandos outfitted with a fleet of helicopters and all-terrain vehicles, they launched surprise inspections across the Iraqi desert, uncovering ballistic missiles and VX nerve gas.

Helped by hundreds of cameras and air sniffers installed at more than 750 sites, they got Iraq to admit to a biological weapons program and were able to tightly monitor materials that could be used for military purposes.

While more than 120 people worked in the field, hundreds of experts and analysts in New York and Vienna pored over their findings and swapped intelligence with select governments chiefly the United States.

But the operation began to unravel by 1996 as Iraq and the inspections teams faced off over access and transparency. Inspectors accused Iraq of violating resolutions and refusing to cooperate with some inspections.

The Iraqis accused inspectors of the same, pointing to wording in resolutions calling on monitors to respect the country’s sovereignty.

The inspectors also complained they were spied on while Iraq claimed the entire operation was a front for U.S. intelligence.