UNITED NATIONS -- Evidence that Iraq has weapons of mass destruction is inconclusive, the United Nations' chief weapons inspector told the Security Council yesterday, thrusting the UN to the centre of the war on terrorism as the U.S. President prepares to make a case for toppling the Iraqi leader.

Hans Blix, head of the weapons-inspection team, played down the significance of recent satellite photos showing reconstruction at Iraqi sites that had been previously identified as nuclear-weapons facilities.

U.S. officials seized on the images as fresh evidence that Iraqi President Saddam Hussein is still trying to build bombs. Mr. Blix was less certain: "Satellites don't see through roofs. So we don't draw any conclusions from them."

An aerial photo may be a valuable clue as to where to inspect, "but we do not draw any conclusions there are weapons of mass destruction from it," Mr. Blix told reporters after a private meeting with Security Council members.

He said it is important for Iraq to allow UN inspectors to return for the country's own sake, so that Baghdad can show it is complying with Security Council resolutions to end its efforts to make nuclear, biological and chemical weapons.

If Iraq complies, inspectors can be on the ground fast after being ejected almost three years ago. But it will take about a year of work before teams can verify that Iraq is not building weapons, Mr. Blix said.

A positive report from the inspectors would clear the way for the UN to lift economic sanctions, Mr. Blix said. "We see inspection as an opportunity [for Iraq], not as a penalty."

Whether the White House has the patience is an open question. Mr. Bush says he wants "a regime change" in Iraq, and his officials have said the sooner the better. The President will make his case for action on Iraq to the UN tomorrow, after a year in which the world body stayed on the sidelines of the war on terror.

But even Britain, the country that has aligned itself most closely with Mr. Bush's Iraq policy, indicated yesterday that it does not want Washington to act unilaterally.

"The important thing on Iraq is for the UN route to be taken and to work. And I hope that the President will make clear that he too believes that," Sir Jeremy Greenstock, the British ambassador to the UN, said.

He was optimistic that Mr. Bush's much-anticipated speech will spur the UN into imposing a deadline for Iraq to comply with requirements to co-operate fully with inspections. The conditions were set after its defeat in the 1991 Persian Gulf war

Sir Jeremy and other Security Council sources threw cold water on news reports that council members are already gearing up for a new war with Iraq.

Many UN diplomats and officials were heartened that Mr. Bush is sensitive enough about world opinion to use the UN to make his first public pitch for action against Iraq.

From their perches atop the 38-storey UN building, international bureaucrats squinted and peered across the Manhattan skyline in disbelief as the twin towers of the World Trade Center collapsed a year ago this morning.

Some felt the entire system of peaceful global co-operation and conflict resolution through diplomacy, the very reasons for the UN's existence, might be falling apart too. It has not been an easy year for the UN. Member countries scrambled to deal with the new antiterrorist agenda and a U.S. administration that didn't want to hear equivocation about how to fight the battle.

Wegger Strommen, Norway's UN ambassador, said the world body acquitted itself fairly well in the immediate aftermath of the Sept. 11 attacks. On Sept. 28, the council unanimously adopted a resolution requiring all states to suppress the financing of terrorism, criminalize fundraising and other material support for terrorist groups, freeze assets immediately, deny terrorists safe haven and notify other countries of any information that those countries might be attacked.

Member countries are required to issue public reports about what they are doing to comply with the resolution.

He and other diplomats note that the resolution swept through the council without suffering the fate of earlier proposals: slow suffocation in a semantic quagmire about the definition of terrorism.