BEIJING, Nov 21 (AFP) - China denied on Monday that one of its coastguard ships used force to retrieve a piece of a rocket floating in the ocean that was being towed by a Philippine vessel in the South China Sea.

A Philippine military commander said earlier the Chinese coastguard ship "forcefully retrieved" the object by cutting a line attaching it to a Philippine boat.

China's foreign ministry spokeswoman Mao Ning told a regular briefing that the object was debris from a rocket's payload fairing - casing that protects the nose-cone of a spacecraft - launched by China.

"People from the Philippines side salvaged and towed the floating object first. After both sides had a friendly negotiation at the scene, the Philippines handed over the floating object to us," Mao said.

"It was not a situation in which we waylaid and grabbed the object," Mao said.

Vice Admiral Alberto Carlos, commander of the Philippine Western Command, said in a statement authorities sent a vessel to examine the object after it was spotted early on Sunday about 800 yards (730 metres) west of Thitu island.

The team tied the object to their boat and started towing it before the Chinese vessel approached and blocked their course twice before deploying an inflatable boat that cut the tow line, then took the object back to the coastguard ship, Carlos said.

The incident occurred as U.S. Vice President Kamala Harris arrived in the Philippines on Sunday for talks aimed at reviving ties with the Asian ally that is central to U.S. efforts to counter China's increasingly assertive policies towards Taiwan.

Harris, whose three-day trip includes a stop on Palawan, an island on the edge of the South China Sea, will also reaffirm U.S. support for a 2016 international tribunal ruling that invalidated China's expansive claim in the disputed waterway, a senior U.S. official said.

China claims most of the South China Sea, through which billions of dollars worth of goods pass each year. Brunei, Malaysia, the Philippines, Taiwan and Vietnam also have claims.

Thitu, known as Pagasa in the Philippines, is close to Subi Reef, one of seven artificial islands in the Spratlys on which China has installed surface-to-air missiles and other weapons.

Thitu, one of nine features the Philippines occupies in the Spratly archipelago, is the Southeast Asian country's strategically most important outpost in the South China Sea.

The Philippine foreign ministry said in a statement it would conduct a thorough review of the incident and was awaiting detailed reports from maritime law enforcement agencies.