US soldiers stand to salute at a ceremony in Baghdad before they leave Iraq. [Chinanews.com]

U.S. President Barack Obama on Saturday signed a massive defense spending bill despite having " serious reservations" with languages on terrorist detention.

The 662-billion-dollar Defense Authorization Act will fund the Department of Defense and some programs of the Department of Energy and Department of Transportation for the 2012 fiscal year starting last October.

"The fact that I support this bill as a whole does not mean I agree with everything in it. In particular, I have signed this bill despite having serious reservations with certain provisions that regulate the detention, interrogation, and prosecution of suspected terrorists," Obama said in a statement accompanying the bill signing.

"My administration will interpret and implement the provisions described below in a manner that best preserves the flexibility on which our safety depends and upholds the values on which this country was founded," he added.

The White House initially threatened to veto the defense bill but later pulled back after Congress made some revisions.

The legislation requires the military to take custody of a suspect deemed to be a member of al-Qaeda or its affiliates, who is involved in plotting or committing attacks against the United States. U.S. citizens are exempted.

However, answering demands from the White House, the bill contains language that says it will not affect "existing criminal enforcement and national security authorities of the FBI or any other domestic law enforcement agency" with regard to a captured suspect, and the president can waive the provision based on national security.