Iraq challenged the United States on Monday to produce "one piece of evidence" that Baghdad is producing weapons of mass destruction.

Iraqi officials also took reporters on two tours in an attempt to refute accusations President Saddam Hussein is rebuilding sites linked to past nuclear efforts and training terrorists.

The head of a U.N. atomic weapons team, Jacques Baute, said Friday that satellite photos show unexplained new construction at several sites the team used to visit when it was still allowed into Iraq for inspections. Baute did not identify the sites in his comments.

British Prime Minister Tony Blair, President Bush's main ally in the Iraq standoff, has cited the satellite photos as proof Saddam had a weapons of mass destruction program that posed a threat.

Iraqi Foreign Minister Naji Sabri said such assessments "are pretexts for ... aggression against our country, they know very well that these are false pretexts, false accusations."

"We challenge them to present one piece of evidence, a single piece of evidence for these accusations," Sabri said.

Bush has threatened Iraq with unspecified consequences if he does not allow the return of U.N. weapons inspectors to certify Iraq is not producing weapons of mass destruction.

Iraq agreed to such inspections after the Gulf War in 1991, but the inspectors left in December 1998 ahead of U.S. and British airstrikes, and Baghdad has not allowed them back.

Sanctions imposed by the U.N. Security Council on Iraq for its 1990 invasion of Kuwait cannot be lifted until the inspectors certify Baghdad has surrendered nuclear, chemical and biological weapons and the missiles to deliver them.

Iraq has denied it still has weapons of mass destruction and has offered only to continue dialogue with the United Nations about the return of inspectors.

U.N. Secretary-General Kofi Annan has demanded that inspectors be allowed to return unconditionally as a first step to further talks.

"We've never put conditions," Sabri said. "We call for the implementation of Security Council resolutions."

The United States not Baghdad, he charged, was preventing the functioning of the U.N. resolutions."

Bush has declared he wants Saddam toppled, but says he has not yet decided whether the United States should attack to achieve that goal.

Sabri pledged that Iraqis would defend their country.

"If we don't have weapons, we shall fight with palm tree branches," Sabri said. "We shall fight with knives, we shall fight with our hands but we shall never allow these colonialists, these invaders to occupy our country."

"This is a religious duty that we defend our honor, we defend our religion, we defend our people."

Monday's two tours brought to six the number of escorted media visits Iraq has conducted in the past month.

Iraqi officials said the site shown to reporters Monday, al-Twaitha, 25 miles south of Baghdad, was one of those referred to by Baute, of the Vienna-based International Atomic Energy Agency.

IAEA spokeswoman Melissa Fleming would not say Monday whether al-Twaitha was one of the locations cited by Baute.

However, she noted that the agency does make annual visits to Iraq for one very limited purpose: to inspect a storage facility at al-Twaitha that contains 1.8 tons of low-enriched uranium and several tons of natural and depleted uranium.

The material is of such low radioactivity that it could not "easily be turned into weapons," she said, and thus it was not seen as necessary that it be removed.

Iraq allows the inspection under the 1968 Nuclear Non-Proliferation Treaty it has signed. The deal, Fleming said, is extremely limited. "It does not allow us to look anywhere other than this particular storage facility," she said.

Iraqi officials said the site at al-Twaitha was destroyed twice, first by the Israelis in 1981 and then by the allies during the 1991 Gulf War.

Saeed Al-Moussawi, a foreign ministry official, escorted journalists around four new buildings at al-Twaitha, dismissing the allegations based on the satellite photos that work on nuclear projects was underway.

Al-Moussawi claimed that the four buildings were used for environmental, medical and agricultural research and "they are purely dedicated for peaceful purposes."

On the other tour, reporters were accompanied by Scott Ritter, a former U.N. weapons inspector who has become a critic of Washington's Iraq policies. He was in Baghdad this week on a trip organized by the Iraqi government.

Ritter supported Iraqi government claims that the camp 25 miles east of Baghdad he visited Monday had been used to train security forces to respond to hijackings. Iraqi dissidents have said it was a terrorist training camp.

"If there is a time and place to go to war [for my country], I will be there," said Ritter, a former U.S. Marine intelligence officer. "But I am not going to go to war based on a fabrication especially from politically motivated Iraqi defectors who intend to misuse the tragedy of Sept. 11 by saying somehow those who perpetrated that crime were trained here."

In a report released Monday, the International Institute for Strategic Studies, a leading independent center for strategic analysis, said Iraq could assemble a nuclear weapon within months if it could steal or buy radioactive material, and it is working to develop equipment to make bomb components.

The report added Iraq has a small force of missiles capable of delivering a nuclear weapon and probably managed to hide some chemical and biological weapons. But it said those pose a limited threat.

Also Monday, the leaders of the two main Kurdish factions that control northern Iraq -- the Kurdistan Democratic Party and the Patriotic Union of Kurdistan -- signed a reconciliation agreement over the weekend.

Sabri sounded confident that Iraqi Kurds would not rebel against Baghdad. "We've our contacts with our brothers in the north. I don't think our Kurdish brothers will accept to be used as pawns against their brothers."