President Bush paid a visit to troops at U.S. Central Command (search) Thursday, proclaiming that the U.S.-led invasion of Iraq was justified and saying that "we'll reveal the truth" on Saddam Hussein's weapons of mass destruction program.

Bush made special note of the recent discovery of what U.S. officials say are mobile biological weapons labs, adding that the search for banned arms could take a long time.

"But one thing is certain: no terrorist network will gain weapons of mass destruction from the Iraqi regime because the Iraqi regime is no more," Bush said with his shirt sleeves casually rolled up as he addressed a sea of desert camouflage-clad U.S. soldiers at the command center for the Iraq war.

"We've made sure Iraq is not going to be used as an arsenal for terrorist groups," he added. Bush's visit comes as questions continue to swirl around his primary justification for the conflict in Iraq -- that Saddam had weapons of mass destruction and was ready to use them.

Bush pointed to the laboratories in a recent interview with Polish television to say, "We found the weapons of mass destruction."

He said Saddam spent decades hiding tools of mass murder and likely got rid of many weapons before coalition troops entered Iraq.

"He knew the inspectors were looking for them," Bush said. "You know better than me he's got a big country in which to hide them. We're on the look. We'll reveal the truth."

The president, fresh from a two-day mission aimed at bringing peace to the Middle East, said the Iraq war "sent along a clear message that our nation is strong and our nation is compassionate."

"America sent you on a mission to remove a grave threat and liberate an oppressed people and that mission has been accomplished," he told the more than 1,000 troops, who cheered every other sentence.

Bush spoke to troops in a warehouse at Camp As Sayliyah (search), the temperatures climbing despite the air conditioning. After his remarks, the president paused to shake his hands with troops. The troops held cameras and video recorders above their heads to get a picture of the president.

Bush offered a broader justification for the war, saying the world is now learning just how great a menace Saddam really was.

"They're learning about the mass graves, thousands of people just summarily executed. They're learning about the torture chambers," the president said. "Because of you, a great evil has been ended."

Earlier Thursday, Bush met privately with U.S. war chief Gen. Tommy Franks and with Paul Bremer (search), the new head of the occupation authority in Iraq, to discuss Iraq's reconstruction.

He also visited the emir of Qatar, a country that has been a longtime U.S. ally. During Operation Iraqi Freedom, the United States used Qatar as its command headquarters for the conflict.

"You have been a steadfast friend of the United States, and for that we are very grateful," Bush told Emir Sheik Hamad bin Khalifa Al Thani.

Bush said Iraq is a better place now, cataloguing humanitarian works by U.S. troops.

The troops are trying to thwart a wave of crime that Bush blamed on Saddam, who he said emptied jail cells of "common criminals" just before the war and left his people hungry and desperate.

The criminals "haven't changed their habits or their ways," Bush said. "They like to rob, loot. ... "We'll find them. Day by day the United States and our coalition partners are making the streets safer for the Iraqi citizens."

Bush blamed Saddam for neglecting his country's infrastructure, without mentioning damage from the war. Building the country up will accelerate the emergence of a new government, he said.

"A more just political system will develop when people have food in their stomachs, and their lights work, and they can turn on a faucet and they can find some clean water -- things that Saddam Hussein did not do for them," Bush said.

Escorted by four F-18 fighters, Air Force One flew over Iraq for over an hour as Bush left the Middle East. The pilot tipped the wings to improve the view from 31,000 feet.

Bush sat on a bench looking out a left-side window with Secretary of State Colin Powell, National Security Adviser Condoleezza Rice and White House Chief of Staff Andrew Card beside him.

Bush seemed pretty familiar with the topography of the area, pointing out landmarks in Baghdad, including two airports, a predominantly Shiite area known as Saddam City and the site of the first night's attack, to his staff.

U.S. and British forces have yet to find hard evidence that Saddam had stocks of chemical and biological weapons.

The president's major ally in the war, British Prime Minister Tony Blair, is accused of exaggerating the dangers posed by Iraq.

But Bush's approval ratings remain high in U.S. polls. His visit to Iraq was his first to the region since combat ended and was similar to a victory lap after a seven-day trip to Europe and the Middle East.

The centerpiece of his trip was the Mideast peace effort. The White House hopes Bush's trips will show the world that the president will pursue peace as vigorously as he pursued the war.

Franks led the war from a high-tech command center at As Sayliyah that was completed just months before the war started. U.S. Central Command held briefings for reporters at a base facility about 12 miles from the capital, Doha.

The Qatari government allowed the U.S. military to stockpile tanks and other combat equipment at Camp As Sayliyah since August 2000 and about 3,000 coalition troops were there during the Iraq war. American forces also flew attack and support aircraft from two air bases in Qatar, al-Udeid and Camp Snoopy.

The Pentagon recently decided to move its air operations center from Saudi Arabia's Prince Sultan air base to Qatar's high-tech al-Udeid facility.

Fox News' Jim Angle and The Associated Press contributed to this report.