WASHINGTON (REUTERS) - The United States will likely transfer additional prisoners from the US naval facility at Guantanamo Bay, Cuba, before President Barack Obama leaves office, the White House said on Thursday (Jan 5).

"I am not able to speak to any specific detainee transfers between now and Jan 20 other than to confirm for you that there are likely to be some," White House spokesman Josh Earnest said at a news briefing.

Obama's final push to shrink the inmate population aims to send as many as 19 prisoners to at least four countries, including Italy, Oman and the United Arab Emirates, before Donald Trump is sworn in on Jan 20.

The Republican president-elect has pressed to halt such releases and has vowed to keep Guantanamo open.

On Wednesday (Jan 4), US officials said there were plans to transfer four detainees from Guantanamo to Saudi Arabia within 24 hours.

Asked about the risk of detainees turning to militant activity against the United States, Earnest said only nine of 183 detainees transferred since Obama took office have been confirmed by the intelligence community as re-engaging in the fight.

He compared that to a 21 per cent rate of return to militant activity of inmates released before 2009.

Earnest credited the low number to a process that required a variety of agencies to certify that appropriate security requirements were in place before an individual was transferred.

If the final transfers go according to plan, only about 40 prisoners will remain at Guantanamo, despite Obama's pledge to close the controversial facility at the US naval base in Cuba.