The United States angered China on Tuesday by sailing a U.S. Navy guided-missile destroyer 12-nautical-miles from their man-made islands in the disputed South China Sea.

A U.S. defense official told Reuters that this was the first in a series of exercises that will test China’s territorial claims. While tensions are rising, the actions of the U.S. are intended to keep the freedom of navigation in one of the world’s busiest shipping lanes.

While the USS Lassen wasn’t met with any resistance, Chinese ships did follow the vessel throughout the South China Sea, and Chinese officials quickly and angrily responded.

“The actions of the U.S. warship have threatened China’s sovereignty and security interests, jeopardized the safety of personnel and facilities on the reefs, and damaged regional peace and stability,” China’s Foreign Ministry said in a statement on its website, according to NBC News.

The “U.S. side [should] think twice, not … take rash moves and stir up troubles,” China’s Foreign Minister Wang Yi warned in a separate statement.

China has reclaimed approximately 2,000 acres of the three main locations in the Spratly Islands located in the South China Sea over the past 18 months. Officials believe that China is building airstrips with the capability of handling bombers. Other countries fighting with China over the territorial claims of the South China Sea include Brunei, the Philippines, Malaysia, Taiwan, and Vietnam. The U.S. has not taken any sides in this dispute.