The U.N. human rights chief says the U.S. government must close the Guantanamo Bay prison as President Barack Obama promised a year ago.

Navi Pillay, the U.N. High Commissioner for Human Rights, says "the facility continues to exist and individuals remain arbitrarily detained -- indefinitely -- in clear breach of international law."

Obama pledged to shutter the U.S. Naval Base prison in Cuba in his annual address to Congress last year.

Pillay said Monday -- ahead of Obama's next annual speech Tuesday -- that she is deeply disappointed the U.S. government "has instead entrenched a system of arbitrary detention."

Pillay said she also is "disturbed at the failure to ensure accountability for serious human rights violations, including torture, that took place."