DAKAR, Senegal (AP) — The U.S. handed over its last military base in Niger — one of two crucial hubs for American counterterrorism operations in the country — to local authorities, the U.S. Department of Defense and Niger’s Ministry of Defense announced in a joint statement on Monday.

The handing over of Airbase 201 in the city of Agadez came after the U.S. troops withdrew earlier this month from Airbase 101, a small drone base in Niger’s capital of Niamey.

U.S. troops have until Sept. 15 to leave the Sahel country following an agreement with Nigerien authorities.

In March, Niger’s ruling junta ended an agreement that allowed U.S. troops to operate in the West African country. A few months later, officials of the two countries announced in a joint statement that U.S. troops would complete their withdrawal by the middle of September.

Niger had been seen as one of the last nations in the restive region that Western nations could partner with to beat back growing jihadi insurgencies. The U.S. and France had more than 2,500 military personnel in the region until recently, and together with other European countries had invested hundreds of millions of dollars in military assistance and training.

Niger’s ouster of American troops following a coup last year has broad ramifications for the U.S. because it is forcing troops to abandon the critical base that was used for counterterrorism missions in the Sahel, a vast region south of the Sahara desert where groups linked to al-Qaida and the Islamic State group operate

One of those groups, Jama’a Nusrat ul-Islam wa al-Muslimin, known as JNIM, is active in Mali, Burkina Faso and Niger and is looking to expand into Benin and Togo.