The US Justice Department has asked a federal court not to allow the release of "dirty bomb" suspect Jose Padilla.
Jose Padilla is currently being held in a military jail
The move comes after an appeal court in New York ruled last month that Mr Padilla, a US citizen seized on US soil, could not be held indefinitely.
Mr Padilla was arrested at Chicago airport and accused of involvement in a plot to set off a radiological weapon.
The Bush administration says his detention as an enemy combatant is necessary for US security.
Deputy Solicitor General Paul Clement filed a request asking for Padilla's release to be put on hold, pending an appeal to the Supreme Court.
Held by decree
Mr Padilla has been held in a naval facility in Charleston, South Carolina, since June 2002 following a presidential decree.
He is thought to be the only US citizen since World War II to be detained on a presidential order.
Last month, a federal appeal court ruled that President George W Bush did not have the authority to hold him in military custody indefinitely.
The court said that, although it recognised that the US Government had a responsibility to protect the nation, presidential authority "does not exist in a vacuum".
The judges said Mr Padilla should be released from military custody within 30 days, but added that the US Government was free to transfer him to civilian jurisdiction.
At the time, White House spokesman Scott McClellan called the court's ruling "troubling and flawed" and said the US Justice Department would seek a stay on the court's ruling and request further judicial review.