By Andrew M. Seaman , AP Beijing — China’s foreign ministry on Monday warned Manila and the Philippines that if they want to stop supplying Beijing with power, then they need to do more than talk.

The ministry said Beijing had informed the two nations that it will suspend power supply to Manila and it would start the process of decommissioning all power stations in the disputed Spratly Islands, an area where Beijing has claimed sovereignty since the late 1980s.

China also said it will conduct a “thorough and serious” investigation into the alleged interference in its internal affairs.

The Philippines has been a U.S. ally for decades, but the Philippines’ relations with Beijing have soured over Beijing’s seizure of several islands and reefs in the South China Sea last year and the Philippine military’s campaign to recapture the South and East China Seas.

Beijing insists it is defending its rights and its own sovereignty in the region.

China has not officially commented on the move.

But it said the two sides have agreed to cooperate on efforts to protect the maritime rights of Filipino fishermen and the national interests of both countries.

The United States has expressed its concerns about the move, which it called “an alarming escalation of the war in the waters around Scarborough Shoal.”

The United Nations has also raised the issue, and Philippine Foreign Minister Delfin Lorenzana said in a statement Monday that “any such violation of international law will be harshly punished and we have been assured of that.”

Lorenzana added that the two countries are cooperating to improve the situation on the Scarborough Shoals.

The islands are strategically important for both countries, as they are linked by water, with overlapping waters in both directions.

China says its reclaimed land is in the Philippines territorial waters, and that the islands were part of its territory from the beginning.

The U.N. Secretary-General’s Special Representative on the South East Asian and Pacific Islands, Jose Miguel Insulza, has urged all countries to take steps to ensure peace and stability in the area.