Iraq's past record of using chemical and biological weapons and hiding them means Saddam Hussein is considered guilty until he proves himself innocent, the White House says.
And he hasn't done so yet, said Press Secretary Ari Fleischer, who added that U.N. weapons inspectors are not reassured by what they have and haven't found.
"Regrettably, they must conclude, as they have done in the past, that the absence of a particular item is not assured," Fleischer said. "So while they have said that there is no smoking gun, they said the absence of it is not assured. And that's the heart of the problem. Iraq is very good at hiding things."
On the other hand, Fleischer said, the inspectors have found that Iraq has illegally obtained or built missile engines, and acquired components of the nerve gas VX. Other citations in the inspectors' report include "discrepancies and inconsistencies" in statements on special munitions and missile engine imports, and inadequate disclosure of the names of people who worked on weapons of mass destruction programs, Fleischer said.
Chief inspector Hans Blix and International Atomic Energy Agency head Mohamed ElBaradei briefed inspectors Thursday on Iraq's 12,000-page weapons declaration.
Blix told reporters that no "smoking guns" have been found in the search for Iraq's nuclear, biological and chemical weapons, but there's no way to know if there are weapons in the country.
"We think that the declaration failed to answer a great many questions," Blix said.
Inspectors omitted the names of scientists known to be involved in their weapons programs, in the report they gave the United Nations and have concluded that the aluminum tubes they found are not suitable for nuclear cetrifuge use, but are suitable as rocket parts. Either use is illegal for Iraq.
Fleischer said the weapons inspectors have raised issues that are real concerns to the United Satates government. Another White House official said the message is "exactly what we have been saying."
Weapons inspectors have until Jan. 27 to hand the United Nations Security Council a formal report on the inspections process. It has often been cited as the date on which the president will decide whether to use military force against Iraq.
That deadline, however, has been questioned by British Prime Minister Tony Blair, who has asked that the inspectors be given a chance to do some work.
"We are in the middle of a process. The U.N. inspectors have just, at the beginning of the year, got their full complement of inspectors there," Blair told government ministers in London, according to his spokesman.
Fleischer said Bush wants inspectors to continue their work in Iraq.
"I've never heard the president put a timeline on it," he said.
After his last briefing to the council on Dec. 19, Blix urged the United States and Britain to hand over any evidence they have about Iraq's secret weapons programs so U.N. inspectors can check it.
Fox News' Wendell Goler and the Associated Press contributed to this report.