Iraqi insurgents in recent days have seized or briefly detained more than 30 hostages from 12 different countries.
Insurgents are kidnapping an increasing number of foreigners in Iraq. As of Monday, Iraqi kidnappers were holding hostage at least one American truck driver, three Japanese - two aid workers and a photojournalist, two Czech television journalists and a Canadian aid worker.
At a coalition briefing in Baghdad, Lieutenant General Ricardo Sanchez would say only that U.S. soldiers and employees of American contractor Kellogg, Brown and Root went missing after a gun fight with insurgents.
"We've got two American soldiers that are unaccounted for at this point, and we also have seven KBR employees that are also unaccounted for," he said.
He did not say whether they were taken hostage or killed.
Kellogg, Brown and Root is an engineering and construction firm which is a subsidiary of oil field services giant Halliburton.
China's official Xinhua News Agency reports that unidentified gunmen have released seven Chinese citizens they had been holding hostage. The Chinese report said the seven men are all safe, but gave few immediate details. Beijing opposed the U.S.-led military invasion of Iraq and refused to send any troops to join the coalition there.
Meanwhile, nine foreigners who drove trucks for military supply convoys were kidnapped, shown in captivity on Arab television Sunday and then released. They are from Pakistan, Turkey, Nepal, the Philippines and India. And eight South Korean missionaries who were held briefly last week either escaped or were released.
Retired Army Major General William Nash says he thinks the recent kidnappings in Iraq are part of an insurgent strategy to cause distractions.
"The insurgents have discovered an opportunity to further complicate coalition activities by seizing vulnerable parties where they might be in order to create diversions from the military operations taking place," he said.
General Nash, currently a senior fellow at the Council on Foreign Relations, says he believes the kidnappers also hope to dissuade various countries from helping with coalition efforts in Iraq. But, he adds, it is too soon to tell whether this goal will be achieved.
"We don't know how various nations will react to it," he said. "But today, it does not look particularly successful because most of the countries won't yield to the demands of the terrorists in such a way as they might want."
The kidnappers holding the Japanese hostages are threatening to kill them unless Tokyo pulls out its several hundred troops from Iraq. Japanese Prime Minister Junichiro Koizumi has said he will not bow to their demands.
Meanwhile, Melissa Winkler, of the International Rescue Committee, says the organization plans to continue its humanitarian work in Iraq despite the abduction last week of Syrian-born Canadian staffer, Fadi Fadel.
"We have not pulled out thus far," she said. "We've continued operating - we've been there for about a year now, keeping a very low profile. And I think for as long as we can, we're committed to staying."
Ms. Winkler says the IRC's humanitarian activities in Iraq include primary health care, sanitation, education and assistance with children - which, she adds, is the work Mr. Fadel was engaged in when he was kidnapped.