Witnesses in the northern Iraqi city said another US soldier was wounded in Monday's fatal drive-by shooting.
The pair had been directing traffic backed up outside a gas station, US Brigadier General Mark Kimmitt said.
He was the 193rd US soldier killed in Iraq since May 1, when US President George W. Bush declared major hostilities over, according to an AFP toll complied from US army reports.
Witnesses said they saw a gunman opening fire on the soldiers with an automatic rifle from the sunroof of a passing black BMW.
"We heard gunshots, we went outside and we saw two Americans lying on the ground bleeding," said the petrol station's owner, Akwan Abdulkarim Mohammad,
Later, four American soldiers travelling in their Humvee vehicle were wounded when a roadside bomb exploded at a traffic light, said Ahmad Talal Mohammed Shiit of the Iraqi police.
A US military spokeswoman in Baghdad said late Monday there were no reports of American soldiers being wounded.
At the United Nations, sources said fellow permanent council members France and Russia led the charge for the handover of the unseen parts of the interim report from the Iraq Survey Group, a team of around 1,400 experts coming the country for banned weapons.
Controversy has raged over whether the Baghdad regime had or was pursuing nuclear, biological or chemical weapons, cited as a main reason for the US-led war that ousted Saddam Hussein earlier this year. The Iraq group's report in October said none had been found so far.
The two countries told the closed-door meeting they want the report to be handed over to UNMOVIC, the UN arms team which monitored Baghdad's weapons programs but left before the start of the war in March.
A US spokesman at the United Nations downplayed the requests and said the US-led coalition in Iraq had been regularly "supplying information" about the hunt for banned weapons.
The call from Russia and France followed a presentation to the council from acting UNMOVIC chairman Demetrius Perricos, who was introducing the latest update report from the still-functioning UN inspection team.
Iraqi and coalition officials meanwhile announced that the interim Governing Council was poised to set up a special tribunal to try allegations of war crimes against officials of Saddam's regime.
Nuredin Dara, a council member, who is himself a judge, told AFP the announcement could come as soon as Wednesday, if the draft statute was approved by the council Tuesday.
He said the current draft foresaw "Iraqi judges with the possibility of foreign judges or experts".
The New York Times reported Monday that the new court would allow no role for the United Nations, unlike tribunals judging war crimes in Rwanda and Sierra Leone.
At the main US base in the southern city of Nasiriyah, sheikhs arrived for talks after Saddam-era land disputes sparked threats of violence among the region's powerful tribes.
Former exiles charge their lands were confiscated during Saddam's brutal Sunni-dominated rule over the Shiite south, and landowners say they have been dispossessed by returnees.
But US commanders stressed they had no powers to adjudicate the disputes themselves -- their aim was purely to defuse the threat of violence between the returnees and those who found a way to cohabit with the Saddam regime.
"Until a new government is formed, we can take no decisions about the ownership of land -- our main priority is to prevent any conflicts arising in the meantime," said US army civil affairs officer Lieutenant Colonel Jeff Bryant.
Khadduri was killed as he tried to defuse an improvised explosive device of the sort favoured by anti-US insurgents.
Colleagues charged that the bomber deliberately detonated the device by remote control as the disposal expert attempted to make it safe.
The coalition-trained Iraqi police have taken a mounting death toll around Baqubah. Twin November 22 suicide attacks killed 13 police and five civilians, according to a US toll.
Kimmitt said there had been an average of 22 attacks a day across Iraq over the previous seven days, 19 of them against coalition troops, but added: "We feel prepared for any upturn in attacks in the days and weeks ahead."
Fifty-one South Korean power workers meanwhile pulled out of Iraq in the face of the growing violence against US allies that last month claimed the lives of two of their colleagues, an embassy spokesman said.
"They decided to go because there was an attack," the spokesman said, asking not be named.
The coalition's civilian spokesman denied their employer, Omu Electric Co, was pulling out of Iraq.
"There has been no withdrawal by that South Korean contractor. There is a security review in that area. We are dealing with security assessments all over the country all the time," coalition civilian spokesman Dan Senor said.