SVAY CHOK, Cambodia (AP) — Cambodia and China began 15-day military exercises on Thursday as questions grow about Beijing’s increasing influence in the Southeast Asian nation.

About 1,315 Cambodian military personnel and 760 Chinese are participating in the regular “Golden Dragon” ground and sea maneuvers, including three Chinese and 11 Cambodian ships.

As the first stage of the exercises got underway at a Cambodian military base with a forested and mountainous training area about 90 kilometers (55 miles) northwest of Phnom Penh, Cambodian army commander in chief Gen. Vong Pisen thanked China for providing new equipment and helping to upgrade military facilities, including the Ream Naval Base.

The United States and others have worried that China’s involvement in building a new pier at the Ream base could lead to it becoming a new outpost for the Chinese navy at a strategically important location on the Gulf of Thailand. As the Golden Dragon exercises began, two Chinese warships had been docked at the pier for more than five months, stoking those concerns.