WASHINGTON -- Of all the leftover business for the Obama administration as U.S. troops prepare to leave Iraq at the end of the year, nothing is more symbolic of the continuing threats there -- and throughout the region -- than the case of a Lebanese Hezbollah operative named Ali Mussa Daqduq.

Daqduq has been one of Iran's top covert operatives in Iraq, according to U.S. officials. He was captured in March 2007 by U.S. forces in Basra who had evidence he had plotted (with Iranian help) a kidnapping in Karbala that January that resulted in the deaths of five American soldiers. U.S. satellite photos showed the Iranians had even built a mockup of the Karbala facility inside Iran to practice the kidnapping.

Daqduq is now a prisoner at Camp Cropper, a U.S. detention facility near the Baghdad airport. Thousands of other detainees have already been released, and the U.S. must close Camp Cropper by year-end, under the status-of-forces agreement negotiated by the Bush administration. The detainees will be handed over to the Iraqis (who would likely free many of them) unless they are transferred elsewhere.

Herein lies the Daqduq conundrum, which has been the subject of weekly interagency meetings this summer: The White House is leaning against releasing a prisoner who has American blood on his hands. But how should he be prosecuted?

The administration is weighing several options. First, Daqduq could be tried by a U.S. military commission, presumably at Guantanamo Bay, under the laws of war. A second option is to try him in a civilian court. That's what the Justice Department decided to do earlier this month with a Somali terrorism suspect named Ahmed Abdulkadir Warsame. He was indicted and transferred to New York for trial, after being held for months in a naval vessel in the Persian Gulf.

The case -- surprise! -- has become something of a partisan political squabble. On July 21, 20 Republican Senators wrote Defense Secretary Leon Panetta urging him not to release Daqduq to the Iraqis and arguing that he should be held at Gitmo and, if possible, tried by a military commission. "If he is released from custody, we firmly believe he will seek to harm or kill more American servicemen and women," the senators wrote.

In a May 16 letter, Republican senators had warned Attorney General Eric Holder against trying Daqduq in a civilian court. "His actions clearly defy the laws of war," they argued.