WASHINGTON – President Obama said Friday that about 100 American troops have been deployed to the African nation of Niger. Two U.S. defense officials the troops would be setting up a base for unarmed drones to conduct surveillance.

Obama announced the deployment in a letter to Congress, saying that the forces “will provide support for intelligence collection and will also facilitate intelligence sharing with French forces conducting operations in Mali, and with other partners in the region.”

The move marks a deepening of U.S. efforts to stem the spread of al-Qaida and its affiliates in the volatile region. It also underscores Obama’s desire to fight extremism without involving large numbers of U.S. ground forces.

The drone base will allow the U.S. to give France more intelligence on the militants its forces have been fighting in Mali, which neighbors Niger. Over time, it could extend the reach not only of American intelligence-gathering but also U.S. special operations missions to strengthen Niger’s own security forces.

One of the two U.S. defense officials who discussed the development confirmed the American troops would fly drones and other surveillance platforms from Niger military airstrips, tracking militant and refugee movement inside Mali and around the border.