US President Barack Obama expressed regret Monday that he hadn't been able to shut down the military detention center at Guantanamo Bay during his eight years in office.

In his first news conference since Republican tycoon Donald Trump was elected to succeed him, Obama blamed the GOP-controlled Congress for his failure to "close the darn thing."

Under Obama, who in 2008 promised to close the jail in his first months in office, the number of suspected jihadists held there has been reduced to 60. 

But Congress refused to permit a group of prisoners still thought to pose a threat to US soil to leave the US naval base in Cuba, and it proved difficult to find countries to host other inmates held without charge.