The U.S. has increasing security concerns about China’s first overseas military base close to the hub of operations for U.S. Africa Command in Djibouti, a U.S. commander told Congress Thursday.

Marine Gen. Thomas Waldhauser, commander of AfriCom, told the Senate Armed Services Committee that he expected the Chinese base on the Horn of Africa to be operational later this summer.

Without getting specific, Waldhauser said he recently met with Djibouti’s President Ismail Omar Guelleh “and expressed our concerns about some of the things that are important to us about what the Chinese should not do at that location.”

The Chinese base would be about four miles from the U.S. base at Camp Lemonnier, one of the Pentagon’s largest and most important foreign military installations, where about 3,000 U.S. military personnel and contractors are assigned to Combined Joint Task Force-Horn of Africa.

Camp Lemonnier is also home to Special Operations Command (Forward) - East Africa, which has carried out operations against Al Shabab militants in Somalia and the Al Qaeda in the Arabian Peninsula group in Yemen.

Personnel at Camp Lemonnier have been involved in highly secretive missions, including targeted drone killings in the Mideast and the Horn of Africa, and in the Jan. 29 raid in Yemen in which Navy SEAL William “Ryan” Owens was killed.

Waldhauser said he expected the Chinese base in Djibouti to support China’s naval presence in the region. He also noted that China has about 2,200 troops in international peacekeeping operations on the continent.

The Chinese military base will be part of a major Chinese port development project in Djibouti. The Chinese Merchants Group, a Hong Kong conglomerate, announced a $400 million investment in Djibouti last November to develop a free trade zone.