BEIJING, March 31 -- China on Monday warned the Philippines about escalating provocation, as the Southeast Asian country stepped up confrontation with China on the South China Sea.

The Philippine side must take consequences of its provocation, said Foreign Ministry spokesman Hong Lei.

By pushing forward international arbitration, the Philippines are attempting to disguise their illegal occupation of Chinese territory. "It is political provocation based on abuse of international law," Hong said at a daily news briefing, reiterating that China will neither accept nor participate in international arbitration.

The spokesman reiterated that China has indisputable sovereignty over the Nansha Islands and adjacent waters.

He noted that China made a statement in accordance with the UN Convention on the Law of the Sea (UNCLOS) in 2006, pointing out that such disputes are not subject to arbitration.

The Philippines sent a ship to the Ren'ai Reef on Saturday with journalists on board, and on Sunday filed a formal plea with an international tribunal.

Taking journalists to the reef was a "deliberate" action to stir up the South China Sea issue in an international court, and another chapter in the Philippines' illegal attempt to seize the reef, Hong said.

It shows once again the essence of the South China Sea dispute between the two countries is sovereignty over islet and reef, not subject to arbitration by the UNCLOS, said Hong.

China will never allow the Philippines to occupy the Ren'ai Reef in any form. China will never allow the Philippines to succeed in its attempt to build facilities there against the Declaration on the Conduct of Parties in the South China Sea (DOC), Hong said.

In Washington, U.S. State Department deputy spokeswoman Marie Harf backed the Philippines' action, saying "all countries should respect the right of any states party, including the Philippines, to avail themselves of the dispute resolution mechanisms provided for under the Law of the Sea Convention."

Hong reminded the U.S. to remember its commitment that it is not a claimant in the South China Sea dispute and does not take position. "We urge the U.S. to stick to its commitment and do more to contribute to regional peace and stability, rather than the opposite."

The Philippines grounded a warship near the Ren'ai Reef in the South China Sea in 1999 and have since refused to retrieve the ship. In a recent statement, the Philippine side claimed that the stranded warship has served as a permanent installation since 1999. The Philippines have also repeatedly attempted to deliver construction materials and build on the reef.