US President Barack Obama announced on Tuesday a plan to create the world's largest marine preserve in the central Pacific Ocean, expanding the Pacific Remote Islands Marine National Monument from about 87,000 square miles to nearly 782,000 square miles. And the biggest protected area ever will extend for 200 miles into the sea. The US government will prohibit fishing, drilling and other commercial activities in the sanctuary and some remote uninhabited islands and atolls.

Uncle Sam has struck a rather novel maneuver by announcing the establishment of a large marine preserve and the international community has yet to figure out which international law it is based on. Washington has not ratified the United Nations Convention on the Law of the Sea (UNCLOS). Hence, it appears that it is seeking to safeguard its rights and interests within its 200-mile exclusive economic zone, a right enjoyed by signatories to UNCLOS. Whether Washington has other purposes remains to be seen.

Protecting sea areas is a highly noble justification, which, nevertheless, should be achieved via legal means. It seems that the US intends to break through some restrictions with the excuse of "protecting the ocean" to further expand and intensify its presence in the Pacific Ocean.

Obama announced the plan to create the largest marine sanctuary amid the process of intense negotiations on the Trans-Pacific Partnership Agreement dominated by Washington. A myriad of world media outlets have simultaneously mentioned these two actions, demonstrating that the whole of the international community has sensed they are somewhat internally linked.

Washington boasts the greatest strategy-designing and implementing capacity in international affairs. It has always been able to perceive what other countries fail to see and conceal what it is reluctant to let others see. While it may prove difficult, China should prompt the international community to demand the US interpret this decision. After all, the preserve will be established on the high seas instead of in its exclusive economic zone. It needs to tell the rest of the world what international laws it is observing.

Japan may be the first victim of the creation of its ally's marine sanctuary because most of the tuna the Japanese people are so fond of are caught from that area. Now, there is little influence over Beijing, but it will probably wield negative impacts in the future.

The US remains highly vigilant against China's maritime activities. There have frequently been voices of opposition against the Chinese navy appearing beyond the first island chain to echo Tokyo's displeasure.

US military bases and the islands it controls are scattered across the Pacific Ocean. Therefore it must aim to tighten the screws on the whole ocean by drawing up plans around them. If the US can arbitrarily change the attributes of high seas and the international community leaves it unchecked, it will certainly do harm to China's interests.