The United States is determined to close the Guantanamo Bay military prison, US Secretary of State Hillary Clinton said here Tuesday, despite delays in shuttering the compound.

"We are absolutely committed to closing Guantanamo. It's turned out to be a little more challenging than we had hoped when we set that goal," Clinton said during a press conference with Spanish Foreign Minister Trinidad Jimenez.

"But there is no doubt about our commitment. And the continuing support from friends like Spain will enable us to keep moving in that direction," Clinton said as she thanked Madrid for accepting three prisoners from Guantanamo Bay.

One of US President Barack Obama's first acts on taking office in January 2009 was to vow to close Guantanamo Bay, which he sees as a prime recruiting tool for Al-Qaeda militants, within a year.

However, two years has lapsed and the prison is still open.

Citing legal and legislative hurdles, the White House admitted in December it would be unable to shut Guantanamo Bay in the near future.

The prison opened at a US naval base in Cuba on January 11, 2002 to house "war on terror" prisoners captured in the wake of the September 11, 2001 attacks.

Following the attacks, which killed almost 3,000 people in New York and Washington, the United States ramped up military efforts in Afghanistan and elsewhere around the world to combat global terrorism.