WASHINGTON - The last American prisoner in Iraq, a Hezbollah commander linked to the kidnapping deaths of five U.S. soldiers, was turned over to the Iraqi government Friday, the White House said.

U.S. officials have long feared that such a transfer would lead to Ali Mussa Daqduq's release from prison. But his case became enmeshed in both international diplomacy and the Washington political debate over how best to prosecute suspected terrorists.

Under President George W. Bush, prosecutors had planned to someday charge Daqduq in a U.S. criminal court. But those plans were scrapped after President Obama took office and lawmakers began restricting the president's ability to bring terrorist suspects into the U.S. for trial.

Many Republicans had wanted Daqduq prosecuted before a military tribunal at the Guantanamo Bay base in Cuba. The Obama administration had hoped a compromise would be to prosecute Daqduq in a first-of-its-kind military commission on U.S. soil. But the Iraqis would not let the U.S. take Daqduq out of the country for trial, White House spokesman Tommy Vietor said.

"We have sought and received assurances that he will be tried for his crimes," Vietor said Friday.

It was not immediately clear what charges he could face. The U.S. has said he was part of a brazen raid in which five American soldiers were abducted and killed in the Iraqi holy city of Karbala in 2007.

Iraq has had a shoddy record on detainee security. Last year, just a week after the U.S. turned more than 1,000 detainees at its Camp Cropper prison over to Iraqi control, four al-Qaeda-linked detainees escaped. An investigation showed that the detainees had inside help.

That had lawmakers worried that Daqduq would return to Hezbollah soon after his transfer.

Sen. Saxby Chambliss (R., Ga.), vice chairman of the Senate Select Committee on Intelligence, fumed over the release of Daqduq. "Rather than ensure justice for five American soldiers killed by Hezbollah terrorist Ali Musa Daqduq, the administration turned him over to Iraq. . . . I expect it is only a matter of time before this terrorist will be back on the battlefield."

Two Iraqi officials, speaking on condition of anonymity said Daqduq was in the custody of Iraqi judiciary authorities in Baghdad. Daqduq will stand before an Iraq investigative judge, one official said.