Obama Administration officials say they have tried to shore up Tunisia's fledgling democracy and position the country as a key counterterrorism partner in the region. Though the drones operating out of Tunisia currently conduct only surveillance missions, US officials said they could be armed in the future, if Tunisia gives the United States permission. The Tunisian Embassy in Washington declined to comment.
The US military has other drone bases on the African continent, from Niger to Djibouti. But officials said they were too far from populous areas on the Libyan coast to be useful in day-to-day counterterrorism operations there. The longer drones have to travel to reach their destinations, the less time they have to "loiter" over their targets.
For lethal strikes in Libya, the US military has relied on manned US aircraft based in Europe and armed drones flown out of Naval Air Station Sigonella on the Italian island of Sicily.
Sigonella is relatively close to Sirte, but flights from the base are routinely cancelled because of cloud cover over the Mediterranean and other weather-related issues, officials said.
US logistical concerns about using Sigonella and other bases in Europe for operations in North Africa prompted the Pentagon's push for a facility on Tunisian soil.
The Obama Administration has kept its negotiations over access to the base secret for more than a year because of concerns that Tunisia's young democracy, worried about being closely associated with an outside military power, would pull out of the talks, or that militants would step up attacks in the North African country.
Isis has already claimed a number of attacks in Tunisia over the last two years, including the killing of dozens of foreign tourists at a beach resort in 2015.
Defence officials said the Pentagon has deployed about 70 military personnel to Tunisia to oversee drone operations there.
As part of the new arrangements, the Obama Administration agreed to share intelligence from the Reapers with Tunisian security forces to help them improve border security. But so far, the United States has made drone flights inside Libya the priority.