BEIJING, July 15 -- China on Tuesday urged "countries outside the region" to stay out of disputes over the South China Sea after a U.S. official proposed that claimants freeze actions which could change the status-quo in the region.

In response to U.S. Deputy Assistant Secretary of State Michael Fuchs's remarks, Chinese Foreign Ministry spokesman Hong Lei said, "China has irrefutable sovereignty over the Nansha Islands and their adjacent waters."

Last week, Fuchs told a Washington think tank that the United States has called for claimant states to voluntarily freeze certain activities on controversial islands and reefs that could change the status-quo in the South China Sea.

Hong said certain countries have illegally seized some of China's islands and reefs since the 1970s and that China has demanded the countries withdraw all their personnel and equipment from there.

"Regretfully, certain countries have strengthened their illegal presence through construction and increased arms build up to infringe on China's territorial sovereignty and maritime rights," Hong said, "to which the Chinese side is firmly opposed."

Hong said China would resolutely protect its territorial sovereignty and maritime rights and is always committed to resolving disputes with countries directly involved through consultations and negotiations, on the basis of respecting historical facts and international law, with a view to safeguarding peace and stability in the region.

Quoting the Declaration on the Conduct of the Parties in the South China Sea (DoC), which was signed in 2002 by China and the Association of Southeast Asian Nations (ASEAN), Hong said all sides promised to exercise self-restraint, not to take moves that may complicate the issue, and handle disputes in a constructive way.

China and the ASEAN countries are effectively implementing the DoC and steadily pushing ahead with consultations for a Code of Conduct (CoC) in the South China Sea, said the spokesman.

"(We) hope that countries outside the region strictly maintain neutrality, clearly distinguish right from wrong, and substantially respect the concerted efforts of the countries in the region to safeguard regional peace and stability," he added.