On a dangerous mission far from home, American soldiers played volleyball and ate turkey for Thanksgiving while remembering comrades slain by insurgents. A U.S. commander warned troops to watch their friends because suicides were on the rise.

"Check on your buddy," Lt. Col. Harry Nantz told soldiers Thursday, urging them to be vigilant for signs of depression.

Their tents and dormitories in a military compound, next to Baghdad's Mother of All Battles Mosque (search), were decorated with papier-mach'e turkeys and orange streamers. The soldiers marked the day with sports and a concert.

Since April, at least 17 Americans — 15 Army soldiers and two Marines — have taken their own lives in Iraq, the military said. At least two dozen non-combat deaths, some possible suicides, are under investigation, according to a review by The Associated Press of Army casualty reports.

The military sent a 12-person mental health team to Iraq to see what can be done to help troops cope with anxiety and depression. The team completed its mission and is expected to make recommendations soon.

Underscoring the continuing violence, a U.S. military convoy came under attack Thursday on the main highway west of Baghdad near the town of Abu Ghraib, witnesses said. An Associated Press Television News cameraman filmed two flatbed military trucks abandoned with cabs ablaze as dozens of townspeople looted tires and parts. The military had no information.

In the northern city of Mosul (search), unidentified gunmen shot dead an Iraqi police sergeant, Brig. Gen. Muwaffaq Mohammed said.

Amid the violence, President Bush made a surprise visit to American troops in Baghdad, flying secretly to Iraq to thank U.S. forces for serving there. It was the first trip ever by an American president to Iraq — a mission tense with concern about his safety.

"You are defending the American people from danger, and we are grateful," Bush told 600 soldiers, stunned and delighted by his visit.

Some 434 U.S. service members have died since military operations began in March in Iraq, the Pentagon says. Of those, 298 died as a result of hostile action and 136 died of non-hostile causes.

Earlier in Baghdad, Thanksgiving runners raced a rain-swept course through avenues and alleyways of Saddam Hussein's old palace complex, now the heavily fortified headquarters of the Coalition Provisional Authority (search).

"Last year, I spent Thanksgiving and did the turkey trot in Austin, Texas. I never thought that one year from then I would be doing the camel trot in Baghdad. So who knows where I'll be next year," said Dan Senor, a spokesman for the U.S.-led civilian administration in Iraq.

In Saddam's hometown of Tikrit, thousands of American soldiers celebrated Thanksgiving listening to live rock music and jogging across a sandbagged camp dotted with bomb-shattered palaces.

Sgt. 1st Class Gary Brimmer of Hart, Mich., said he misses his wife and three children but considers himself lucky. A distant cousin, Sgt. Todd Robbins, was killed in Iraq earlier this year by what he said was "friendly fire."

"I think of him a lot, a fine man. He paid the ultimate price. The price I have to pay for not being with my family is small in comparison," said Brimmer, panting after bagging the gold medal for finishing ahead of 449 other soldiers in a "turkey trot" foot race.

Addressing troops in Mosul, Maj. Gen. David Petreaus, commanding general of the 101 Airborne Division, said: "I am happy to see the end of November. We've taken some real blows during this time. We've had some terrible losses."

"The fact is that we have taken some hard shots, but winners and champions do get knocked down every now and then, and the test of a champion is whether you get back on your feet and start swinging again. And that's exactly what we've done," the commander said.

On the political front, U.S.-led efforts to transfer power to a transitional Iraqi government ran up against a major obstacle after key figures in the powerful Shiite Muslim leadership criticized the handover blueprint — and the Kurdish president of the U.S.-picked Iraqi Governing Council said he agreed with the criticism.

Iraq's most influential Shiite leader, Grand Ayatollah Ali Husseini al-Sistani (search), objected the plan's call for electing a transitional legislature from regional caucuses. Instead, he demanded a transitional legislature that would be elected directly.

Jalal Talabani, who signed the plan as head of the Iraqi Governing Council (search) on Nov. 15, traveled to the holy city of Najaf to meet al-Sistani, and said he thought the cleric's views were "logical and reasonable."

Talabani planned to discuss them with his colleagues on the council and the U.S.-led coalition, he said.

"The agreement remains, but we may add an attachment that has additional clauses," said Talabani, a Sunni Muslim. "The agreement can evolve ... I will take his views to the council and we, God willing, hope to ratify them."

The U.S.-led coalition declined comment on al-Sistani's views and a spokesman, speaking on condition of anonymity, said the head of the administration, L. Paul Bremer, had no wish "to negotiate in public."