BAGHDAD (Reuters) - President Bush secretly traveled to Baghdad and paid a surprise Thanksgiving Day visit to U.S. troops on Thursday in a bold mission to boost the morale of forces in Iraq amid mounting casualties.

In an elaborate plan to ensure his security, Bush slipped away from his Texas ranch on Wednesday night, arrived in Iraq on Thursday and spent 2-1/2 hours with the troops.

"I bring a message on behalf of America: We thank you for your service, we are proud of you and America stands solidly behind you," Bush told about 600 soldiers, who were stunned to see the president emerge from a side door inside a military mess hall at Baghdad International Airport.

Bush dropped plans to eat the traditional turkey dinner with his wife and family in order to visit U.S. troops in the Iraqi capital, making him the first U.S. president ever to visit Iraq.

The troops, mostly from the U.S. Army´s 1st Armored Division and the 82nd Airborne, had no idea Bush would be there.

Without hinting of the enormous surprise to come, Iraq´s U.S. civil administrator Paul Bremer told the soldiers he was supposed to read the president´s Thanksgiving proclamation to them but would instead defer to the most senior person on the premises.

At that point, Bush emerged wearing a military jacket and loud cheering began.

"I was just looking for a warm meal somewhere," Bush said. "Thanks for inviting me to dinner ... I can´t think of a finer group of folks to have Thanksgiving dinner with than you all."

Six months after he declared major combat operations over in Iraq with a controversial visit to an aircraft carrier, only to see a guerrilla insurgency ensue, Bush vowed to stay the course.

With the U.S. economy perking up, Iraq is emerging as perhaps the greatest threat to Bush´s re-election in 2004.

"You are engaged in a difficult mission. Those who attack our coalition forces and kill innocent Iraqis are testing our will. They hope we will run," he said.

"We did not charge hundreds of miles through the heart of Iraq, pay a bitter cost of casualties, defeat a ruthless dictator and liberate 25 million people only to retreat before a band of thugs and assassins," the U.S. president said to a standing ovation.

"We will prevail. We will win because our cause is just. We will win because we will stay on the offensive," Bush declared.

Afterward Bush shook hands with soldiers, all of them wearing desert fatigues and took a place in the chow line and helped serve them plates of food.

Bush also met with four members of the Iraqi Governing Council, the U.S.-appointed group that has struggled to return normal life to Iraqis and is drawing up plans for free elections and a constitution.

Bush stayed at the heavily guarded Baghdad airport for a total of two hours and 30 minutes before flying back to Washington and then on to Texas.

From start to finish, Bush´s trip took about 30 hours, 27 of them spent in the air. Accompanying him were a handful of top aides, a contingent of U.S. Secret Service agents and a small group of reporters, all sworn to secrecy.

The mission was a closely held secret at the White House known only by a handful of senior aides. Aides said Bush made the decision to go five or six weeks ago while on a trip to Asia.

He informed Vice President Dick Cheney, White House chief of staff Andrew Card and national security adviser Condoleezza Rice in a video conference call on Wednesday.

It was so secret that Bush´s parents, former President George Bush and Barbara Bush were not told.

Bush only told his wife where he was going hours before leaving and informed his daughters, Barbara and Jenna, just before departing.

Bush was smuggled off his Crawford, Texas, ranch in an unmarked vehicle without his usual motorcade for a 45-minute drive to Texas State Technical College airport in nearby Waco.

White House communications director Dan Bartlett would not say how Bush was whisked off the ranch.

"If you were outside the ranch waiting for the president, you would not have known that the president just left," he said.

At the Texas airport, Bush departed aboard his presidential 747 aircraft, Air Force One. The cover story was the plane was being taken to Washington for maintenance. He entered the rear of the plane. The aircraft´s lights were dark as it flew.

Upon landing at Washington´s Andrews Air Force Base, this plane was rolled into a giant, heavily guarded hangar where an identical plane awaited. Bush switched to the second jet for the Baghdad flight.

As he boarded, he turned to reporters accompanying him, held one hand to his ear as if he were holding a cellular phone, made a cutting motion across his neck with the other and mouthed the words, "No calls." (© Reuters 2003 11/27/03)