Chinese coast guard vessels. (Source: SINO DEFENCE)

An amendment to China's Maritime Traffic Safety Law—put into practice on Wednesday—requires foreign vessels to report information such as their name, call sign, current position, destination and cargo before sailing through what it claims as its "territorial sea."

Reached by Newsweek, Defense Department spokesperson John Supple said, “The United States remains firm that any coastal state law or regulation must not infringe upon navigation and overflight rights enjoyed by all nations under international law.”

"Unlawful and sweeping maritime claims, including in the South China Sea, pose a serious threat to the freedom of the seas, including the freedoms of navigation and overflight, free trade and unimpeded lawful commerce, and the rights and interests of South China Sea and other littoral nations," he added.

The free seas principle is codified in the United Nations Convention on the Law of the Sea (UNCLOS)—ratified by China and recognized by the US—and grants to all nations the right of innocent passage through a coastal state's territorial waters. The US maintains that the unilateral imposition of any advance-notification requirement is contrary to international law.

In a separate response regarding the potential impact of China's maritime law on US Navy operations in the region, the Pentagon's Lt. Col. Martin Meiners said, "The United States will continue to fly, sail and operate wherever international law allows."