Allowing Iraq to possibly transfer weapons capability to terrorists was not a risk he was willing to take, Mr. Bush said.
"Although we have not found stockpiles of weapons of mass destruction, we were right to go into Iraq," Mr. Bush said after inspecting a display of nuclear weapons parts and equipment, including assembled gas centrifuges for uranium enrichment, from Libya.
The hardware was shipped here in March as part of an agreement with Moammar Gadhafi to end his country's nuclear weapons program.
The president offered a broad new defense of the March 2003 invasion of Iraq three days after the release of a Senate report that harshly criticized unsubstantiated intelligence cited in the run-up to the war in Iraq, a crucial battle in the war on terrorism.
The key U.S. assertions leading to the 2003 invasion of Iraq — that Saddam Hussein had chemical and biological weapons and was working to make nuclear weapons — were wrong and based on false or overstated CIA analyses, a scathing Senate Intelligence Committee report asserted Friday.
"We removed a declared enemy of America who had the capability of producing weapons of mass murder and could have passed that capability to terrorists bent on acquiring them. In the world after September 11th, that was a risk we could not afford to take," Mr. Bush said.
It is unclear if Iraq had the capability of producing weapons of the type described by Mr. Bush.
The Senate committee said the CIA was right to say Iraq had experience with weapons of mass destruction, but raised doubts about the intelligence the CIA used to assert that Baghdad retained the capacity to make chemical or biological weapons.
Without directly acknowledging the intelligence was flawed, Mr. Bush said a wide array of government leaders, from members of the Clinton administration to lawmakers to the U.N. Security Council, had studied the same intelligence and "saw a threat."
During the Clinton administration, official U.S. policy toward Iraq became "regime change" — a stance that sought the ouster of Saddam Hussein, he noted.
But Saddam refused to open his country to inspections, Mr. Bush said.
"So I had a choice to make: either take the word of a madman or defend America. Given that choice I will defend America."
Mr. Bush has used similar rhetoric in speeches for months, but the words took on added significance in light of the latest report condemning the Iraq intelligence.
Mr. Bush's trip to Tennessee was designed to showcase a victory in his administration's campaign against weapons of mass destruction.
Mr. Bush was shown nuclear weapons parts and equipment from Libya, and called them "sobering evidence of a great danger." It was the White House's second effort to shine a spotlight on the Libyan victory. Several months ago, the White House arranged a tour for journalists of the equipment.
Mr. Bush said Libya's decision to scrap its nuclear ambitions and do away with its long-range missiles was the result of "quiet diplomacy" by the United States, Great Britain and the Libyan government. But it also was the result of outspoken public denunciations of nations that seek to threaten the world with nuclear and other weapons, he said.
He said the world knows that doing so carries serious consequences and that the "wise course is to abandon those pursuits."
And Mr. Bush said his administration was doing everything possible to avert the attacks he said terrorists are now plotting.
The Senate report released Friday looked only at the performance of intelligence agencies, not whether Bush administration officials exaggerated the reports the CIA gave them.
The White House's role will be examined in a second phase of the committee's investigation, which probably will not be finished until after the election.
The ranking Democrat on the intelligence committee, West Virginia Sen. Jay Rockefeller, said the administration should be held partly accountable for what he considered to be an undue interest in invading Iraq after the Sept. 11, 2001, attacks.
"In the meantime, we have created, therefore, the lowest standing of the United States in our history around the world; more people trained and being trained for probably a generation or so to come to hate us and to try and hurt us abroad and here in the homeland," the Democrat said.
But committee chairman Sen. Pat Roberts, R-Kan., said the White House should not be blamed for asking tough questions of analysts and making public statements such as those referring to a "mushroom cloud" — which is produced after a nuclear explosion — in describing the Iraqi threat.
"The information that was provided to the president and to the Congress — that led to the same kind of assertive comments that the same critics are now blaming the president for — was flawed," he said.