MANILA (AFP) - The Philippines pledged to act with restraint on Friday a week after China tried to block a boat ferrying supplies to Filipino troops on a disputed reef in the South China Sea.

"(The) Philippines makes clear that it will continue to exercise self-restraint and will not raise tension in the South China Sea," Foreign Secretary Albert del Rosario said.

He issued the statement after a week of diplomatic wrangling following a Philippine boat's delivery of food, water and fresh troops to Second Thomas Shoal, also claimed by Beijing, by slipping through a blockade by two Chinese coastguard vessels.

A small number of Filipino soldiers are stationed on a Navy vessel that was grounded on the shoal in 1999 to assert the Philippines' sovereignty.

A day after the incident, the Philippines further infuriated China by asking a United Nations tribunal to declare Beijing's claims to undisputed sovereignty over most of the strategically important sea as illegal.

China strongly criticised the Philippine government actions, warning on Tuesday that the UN appeal had "seriously damaged" bilateral ties and holding Manila responsible for the "consequences" of the UN move.

"The Philippines is not the country that has greatly increased its naval and maritime presence in the South China Sea," Mr del Rosario retorted on Friday.

"Nor has it challenged freedom of navigation. Nor has it blockaded nor forcefully intimidated any other country in the South China Sea. Countries should be judged by their actions, not by their words."

China has said its coastguard turned away another Filipino vessel on a similar resupply mission early last month, forcing the Philippine military to air-drop supplies to its small unit of marines aboard an old navy ship guarding the reef.

The reef lies 200km from the nearest major Philippine island, and more than a thousand kilometres from a major Chinese land mass.

It is part of the Spratlys, a chain of islets and reefs that sit near key shipping lanes and are surrounded by rich fishing grounds.

Apart from China and the Philippines, Brunei, Malaysia, Taiwan and Vietnam also have overlapping claims to parts of the area.

Manila's UN appeal argues Beijing's claims are contrary to the UN Convention on the Law of the Sea (UNCLOS) and interferes with the Philippines' sovereign rights to its continental shelf.

Both countries are signatories to UNCLOS, but Beijing argues that its provisions do not apply to the row.

It has urged the Philippines to negotiate directly with it.

Mr Del Rosario said on Friday that UN arbitration "is a peaceful, friendly and a durable settlement mechanism under international law" that allows the Philippines to defend "what is legitimately and rightfully ours".