The United States military should set a date to begin withdrawing troops from Iraq so Iraqi officials can make plans to take over security and other duties there, U.S. House Homeland Security Chairman Bennie Thompson said Friday.

The Mississippian and two other Democratic members of Congress— G.K. Butterfield of North Carolina and Allyson Schwartz of Pennsylvania — spent about 12 hours in Iraq on Friday, touring military operations and meeting with U.S. officials at the embassy in Baghdad.

After the tour, Thompson spoke to reporters by conference call from Kuwait. He said the top U.S. commander in Iraq, Gen. David Petraeus, made “a strong argument” for more American military investment there.

Thompson said Petraeus told the congressional delegation that if the U.S. is successful in Iraq, “many of the challenges that could confront the homeland will be reduced.”

Asked if he agrees with that assessment, Thompson said: “I am still of the opinion that many of the reasons that brought us to Iraq did not materialize from a truth standpoint, but we’re there.”

Thompson said the Department of Homeland Security and the State Department need to work together more closely on issues such as getting visas for foreigners who want to go to the United States after having helped the U.S. military in Iraq.

He said once enemies know those people want to leave, the helpers could be injured or killed.

“Six, eight, 10 months is too long for you to be a target,” Thompson said.

He said he was interested to see some of the technology that is being used along international borders in Iraq, including machines that use so-called backscatter radiation to scan the entire body.

The backscatter uses a narrow, low-intensity x-ray beam that’s scans the entire body at a high speed. The amount of radiation used during this scan is equal to 15 minutes of exposure to natural background radiation such as the sun’s rays.

Thompson said the backscatter is “fairly intrusive, but it gets the job done.”

The Phoenix Sky Harbor International Airport started using backscatter radiation machines in February 2007. Before the technology can be widely used in the United States, “we have to resolve some privacy issues around it,” Thompson said.

Thompson said while he was in Iraq, he saw members of Mississippi Army National Guard’s 1387th Quartermaster Company. The Greenville-based group is from Thompson’s congressional district. The unit’s 151 members are responsible for providing drinkable water for much of Iraq.

“They were in good spirits,” Thompson said.