U.N. inspection teams are ready to chase down any mobile bioweapons labs, detect underground weapons sites with radar and investigate the "aluminum tubes" Washington says might help Iraq build a nuclear bomb, team leaders said Tuesday.

The U.N. experts have clear — if secret — game plans for the months of inspections ahead, they said.

"We are fully conscious of the responsibility we have on our shoulders," said Jacques Baute of the U.N. nuclear agency.

A working group of 17 inspectors landed in Baghdad on Monday, the first of some 100 who will be operating in Iraq at any one time by the end of the year.

They are here under a U.N. Security Council mandate to resume inspections, broken off in 1998, to ensure that Iraq — as it claims — has no stocks or programs to build nuclear, chemical or biological weapons. A U.S. strike on Iraq may hinge on the new round of inspections, which begins Wednesday.

The U.N. Security Council has warned of "serious consequences" for Iraq if Baghdad is found in major violation of the U.N. disarmament demands. The Bush administration has threatened military action against Iraq in that case, with or without U.N. sanction.

On Wednesday, the U.N. teams will likely revisit an unidentified Iraqi site previously inspected in the 1990s. The inspectors will later branch out to new or rebuilt sites — for example, suspected storage places for chemical weapons U.S. intelligence alleges are still held by Iraq.

Baute, of the Vienna-based International Atomic Energy Agency, and Demetrius Perricos, of the New York-based U.N. Monitoring, Verification and Inspection Commission, met with reporters on the eve of their first field mission to discuss the technical side of the inspections.

Perricos was asked whether the arms monitors will be looking for suspected truck-borne biological weapons laboratories. "We have some plans," he said.

A recent U.S. intelligence report said an Iraqi document indicates the Baghdad government "was interested in developing mobile fermentation units" for biological weapons.

This is "not something we find incredible," Perricos said. He noted that inspectors have the right to stop suspect vehicles on Iraqi roads, but he would not discuss their plans further.

As for possible buried storage or production sites, "we have a strategy for underground facilities" using ground-penetrating radar, Perricos said.

The U.S. government has raised an alarm over what it says are efforts by the Iraqi government to import aluminum tubes of a kind that might be usable for gas centrifuges, equipment that can "enrich" uranium to the level of bomb-grade material. The U.N. nuclear agency has said it is seeking more information from Washington on the tubes, which could also be used for non-nuclear purposes.

Baute said his nuclear team would look into the reported tubes deal "for us to have a clear understanding what the intention was in this area."

British and U.S. officials say they are sure Iraq retains weapons of mass destruction. The U.N. inspectors are to report to the Security Council by late January on their initial round of inspections, including whether the Iraqis have been fully cooperative.

In seven years' work ending in 1998, U.N. expert teams destroyed large amounts of chemical and biological weapons and longer-range missiles forbidden to Iraq by U.N. resolutions after the Gulf War, in which an Iraqi invasion force was driven from Kuwait. The inspectors also dismantled Iraq's nuclear weapons program before it could build a bomb.

Those inspections were suspended amid disputes over U.N. access to Iraqi sites and Iraqi complaints of American spying via the U.N. operation.