Obama said: "We are going to close Guantanamo. We are serious about this."
The president, however, did not repeat the January 2010 deadline he originally set for shutting the facility.
Obama promised soon after taking office to close the prison, arguing that doing so would help restore the U.S. image abroad.
The White House has said it still hopes to meet that deadline. But senior officials have acknowledged it may slip because difficult issues still to be resolved. More than 220 detainees remain at the prison.
