Several coalition nations are sending more experts into postwar Iraq to take over and expand the hunt for weapons of mass destruction (search) amid growing doubts about the country's weapons program.

Maj. Gen. Keith Dayton (search), who is heading the Iraq Survey Group, leaves Monday for Baghdad. The new team of about 1,400 experts from the United States, Great Britain and Australia will replace a smaller U.S. military team -- which so far has found little to corroborate the coalition's assertions on Iraq's weapons in the lead up to the war.

The large new team will shift focus from sites identified as suspicious before the war to areas where documents, interviews with Iraqis and other new clues suggest biological or chemical weapons could be hidden, Dayton said.

The shift comes amid growing questions from allies and some members of Congress about why no chemical or biological weapons have been found. President Bush (search) said Iraq had chemical and biological weapons, as well as a nuclear weapons development program. Bush used the elimination of those programs as justification for waging war against Saddam Hussein's regime.

But The Guardian reported Saturday it obtained a transcript showing that U.S. Secretary of State Colin Powell (search) and his British counterpart, Jack Straw (search), both were privately skeptical about the quality of the intelligence on Saddam Hussein's weapons program although they were using it to sway U.N. Security Council members to support the war.

Before the war, the United States drew up a list of more than 900 "suspect sites" where weapons of mass destruction or evidence of such programs might be found. Military teams have visited more than 200 of those sites without finding any actual weapons.

The United States has found two equipment-filled trailers in northern Iraq that American intelligence agencies say were mobile biological weapons production facilities. Bush and other administration officials say the finds show Iraq did indeed have clandestine programs to make germ weapons.

In response to questions about the credibility of U.S. intelligence, CIA Director George Tenet released a statement Friday defending his agency.

"Our role is to call it like we see it -- to tell policy-makers what we know, what we don't know, what we think, and what we base it on," he said. "The integrity of our process was maintained throughout and any suggestion to the contrary is simply wrong."

Dayton, a top official in the Defense Intelligence Agency, said he remains convinced his team will find chemical and biological weapons in Iraq. He said he believed the information the United States had before the war indicating Iraq had the banned weapons and continues to believe that.

"Do I think we will find something? Yeah, I kind of do," Dayton told reporters at a Pentagon news conference. "This is not necessarily going to be quick and easy, but it's going to be very thorough."

Dayton said the Iraq Survey Group will include 200 to 300 searchers to fan out around Iraq to look for weapons, hundreds of experts to interrogate Iraqis, about 250 people to analyze documents and computer files at a regional base in Qatar and analysts to put the pieces together and figure out what they mean.

Establishment of the group, announced last month, "represents a significant expansion of effort in the hunt for weapons of mass destruction," Dayton said.

The group will begin a two-week transition period to take over the weapons hunt in Iraq no later than June 7, Dayton said.

The group includes both military and civilian experts, including former United Nations weapons inspectors. Stephen Cambone, the Pentagon's top intelligence official, said Friday he did not know whether the United States would agree to have U.N. inspectors return to Iraq.

Critics say the Bush administration should let U.N. inspectors back in.

"Given the size and complexity of the task, it's unwise to turn down help from groups who have demonstrated expertise in this area," said Paul Kerr, an analyst at the Arms Control Association in Washington.

Cambone and Dayton said they did not know why no chemical or biological weapons have been found so far. Dayton echoed comments by Defense Secretary Donald H. Rumsfeld earlier in the week speculating that Iraq could have destroyed such weapons before or during the war.

"These things could have been taken and buried. They could have been transferred. They could have been destroyed," Dayton said. "That doesn't mean they weren't there in the first place."

The Iraq Survey Group also will investigate possible war crimes by Iraqis, links between Saddam's regime and terrorism and the fate of those missing in action or held prisoner since the 1991 Persian Gulf War.

Dayton said those other missions make sense because his team will be interrogating Iraqis who may know about all of those issues and because his analysts will be able to pull together clues on those matters.

"They're all interrelated," Dayton said. "We'll be connecting pieces that haven't been connected before."

The Associated Press contributed to this report.