The United States has warned China of consequences after reports that the country has installed missiles on three of its outposts in the disputed waters of the South China Sea.

“We’re well aware of China’s militarisation of the South China Sea,” AFP quoted Press Secretary Sarah Sanders as saying. “We’ve raised concerns directly with the Chinese about this and there will be near-term and long-term consequences.” Sanders, however, did not elaborate on these consequences.

Pentagon Chief Spokesperson Dana White said China must understand that it “cannot, and should not, be hostile, and understand that the Pacific is a place in which much commerce goes through”, according to CNN. “And it is in their interest to ensure that there’s a free navigation of international waters.”

Chinese Foreign Ministry spokesperson Hua Chunying said the country was involved in peaceful construction in the region. It included the “deployment of necessary national defence facilities”, she said. “The relevant deployment targets no one.”

“Anyone with no invasive intention will find no reason to worry about this,” Hua said, adding that China hopes the “relevant party” could view this matter in an “objective and calm way”. China has “indisputable sovereignty” over the islands, she claimed.

Several countries – China, Philippines, Vietnam, Taiwan, Malaysia and Brunei – have been fighting over the resource-rich South China Sea for years. China has claimed nearly 90% of the territory, which is defined by the nine-dash line, and has also issued a map to back its claims.

In July 2016, an international tribunal in The Hague ruled in favour of the Philippines and said Beijing had no legal basis to claim “historic rights” over the South China Sea. The Permanent Court of Arbitration accused China of breaching the sovereign rights of the Philippines by exploring resources near the Reed Bank. However, the Chinese government called the verdict “ill-founded”. Beijing also said that its “territorial sovereignty and marine rights” in the seas would not be affected by the verdict.