The White House is considering a "wide array" of options for closing the US military prison in Guantanamo Bay, Cuba, spokesman Josh Earnest said on Monday, declining to rule out executive action as an option.
Earnest said the best route for closing the prison would be winning congressional approval to do so.
The facility, where most detainees have been held without trial for more than a decade, has drawn international condemnation for the harsh treatment of foreign terrorism suspects.
But President Barack Obama, who has repeatedly pledged to close the prison, has faced opposition from congressional Republicans who passed laws blocking any move to transfer Guantanamo inmates to prisons in the United States.
Asked if Obama would consider taking executive action to close the prison if Congress blocks him, Earnest said, "The president and his team are always considering a wide array of options.
"But the fact is the best way for us to do this is for members of Congress of both parties to work effectively with the administration," Earnest said.
The White House said last month that it would soon be sending a plan to Congress to close the prison. A unilateral move by Obama to close the prison would be sure to set off a firestorm in Congress.