America's Central Intelligence Agency has been operating a secret airbase for drones in Saudi Arabia for the past two years, BBC reported.
The facility was established to hunt for members of the Yemen-based Al Qaeda in the Arabian Peninsula (AQAP).
A drone flown from there was used in September 2011 to kill Anwar al-Awlaki, a US-born cleric alleged to be AQAP's external operations chief.
US government officials said they were concerned the disclosure about the facility would undermine operations against AQAP, as well as potentially damage counter-terrorism collaboration with Saudi Arabia.
The US military pulled out virtually all of its troops from Saudi Arabia in 2003. There were between 5,000 and 10,000 US troops in the country kingdom after the 1991 Gulf war.
Only personnel from the US Military Training Mission (USMTM) officially remain.
The location of the secret drone base has not been revealed, and the Saudi government has also not made any comment.
Construction was ordered after a December 2009 cruise missile strike in Yemen, the New York Times said.
US officials said the first time the CIA used the secret facility was to kill Awlaki.
Three other Americans, including Awlaki's 16-year-old son, have also been killed in US strikes in Yemen.
The Washington Post said US President Barak Obama's counter-terrorism adviser John Brennan, a former CIA station chief in Saudi Arabia, played a key role in negotiations with the government in Riyadh over building the drone base.