The U.S. military says six people claiming to be Americans and two who say they are British, and who posed a threat to coalition forces, are being detained in Iraq. The continuing threat to American forces posed by foreign fighters entering Iraq prompted the Bush administration Tuesday to deliver another strong warning to Syria about what it considers unacceptable behavior by Damascus.

At the Pentagon Tuesday, Defense Secretary Donald Rumsfeld said a clear picture had not yet emerged about who these eight people are even though they were judged to be a threat to coalition forces.

"The folks that we've scooped up have on a number of occasions multiple identifications from different countries," he said. "They're quite skilled at confusing people as to what their real nationality is or where they came from or what they're doing and it takes a little time to sort those things out."

But Central Command spokesman Major Pete Mitchell stressed that the eight were considered to be dangerous enough to be detained and questioned, even though he considers their claim to be American and British highly suspicious.

"People who are detained will say all different sorts of things and that's human nature and the mission of these people who are doing the interviewing and interrogating are to get to the bottom line and right now we can't say definitively whether these are American or British citizens," he explained.

The British government is investigating the claims as well. The case of the eight marks the first time since the United States and Britain launched the war in Iraq in March that people claiming to be from both nations have been picked up in the country on suspicion of involvement in attacks on coalition forces.

For months, the Bush administration has been alleging Syria has not done enough to stop foreign fighters from entering Iraq and attacking coalition troops. Syria denies the charges. But on Capitol Hill Tuesday, State Department official John Bolton charged Syria has done nothing to change its behavior despite assurances given to Secretary of State Colin Powell during a trip to Damascus in May.

"Syria allowed military equipment to flow into Iraq on the eve of and during the war," he said. "Syria permitted volunteers to pass into Iraq to attack and kill our service members during the war and is still doing so."

That charge was followed up with another unusually strong warning from the White House where a spokesman again put Syria on notice that it would be held accountable if it does not change what the administration characterizes as unacceptable behavior.