Washington and Manila on Monday kicked off their second joint military drill of the year, and analysts warned that the move will bring more uncertainty to regional ties in the wake of the Huangyan Island incident.

The Philippines-US naval training exercises, scheduled from Monday to July 10 near Mindanao Sea, began with US vessels, including the USS Vandegrift, arriving at Makar Port in General Santos City in the southern Philippines on Sunday.

The drill involves 450 members of the Philippine Navy and Philippine Coast Guard, and 500 staff members of the US Navy and Coast Guard.

Dave Welch, commodore of the USS Vandegrift, said the training will include in-port exercises and expertise exchanges, Xinhua reported.

Although the Philippines' armed forces said the drill is an annual routine and "not aimed at any third party", analysts said the exercise benefits the country and further helps the US shift strategic emphasis back to the Asia-Pacific region.

"The drill shows both Washington and Manila's will to beef up their alliance since the 1950s, and Manila has received support from Washington in various areas, especially this year," said Yang Baoyun, a professor of Southeast Asian studies at Peking University.

The US has reiterated that it does not take a position on the rival territorial claims of countries in the South China Sea, but Manila still has expressed its hope that Washington could back its claim to China's Huangyan Island, Yang said.

On April 10, 12 Chinese fishing boats were harassed by a Philippine Navy gunboat while taking refuge from harsh weather in a lagoon near China's Huangyan Island. Two Chinese Marine Surveillance ships in the area later came to rescue the Chinese fishermen from being detained by Philippine naval forces.

Later, Beijing protested Manila's infringement on China's sovereignty, and sent official ships to the spot for a monitoring mission. The drill comes after Manila's announcement on Friday that it had sent observers to the US-led Rim of the Pacific Exercises, the largest-ever naval drill in the region, involving 22 countries.

"The Philippines' decision to join the Monday drill and its involvement in the RIMPAC are aimed at demonstrating its alliance with the US, and it is also showing off strength to China," said Yin Zhuo, a military expert in Beijing.

Yin warned that the recent drills may add rifts between China and the Association of Southeast Asian Nations.

Washington has recently been restrained on issues concerning Manila and the Huangyan Island, and it also hopes to keep China-US ties stable in an election year, said Yuan Peng, an American studies expert at the China Institutes of Contemporary International Relations.

However, the US has continued to resort to high-level consultations with Manila on regional issues after the Huangyan Island impasse.

US Secretary of State Hillary Clinton in early June told Philippine President Benigno Aquino that Washington will continue to monitor the Huangyan Island situation closely.

Beijing on Monday also slammed Manila's recent remarks concerning the Huangyan Island, as reports said the Philippines military vowed to escort Philippine vessels and fishermen back to the island after the Philippine fishing ban ends. "We expect the Philippines to contribute more to facilitate both the ease of the island situation as well as the bilateral friendly cooperative relations," Foreign Ministry spokesman Liu Weimin said at a daily news conference.

Philippine Senate President Juan Ponce Enrile was quoted by Philippine Daily Inquirer on Monday as saying China's claim to Huangyan Island was "legally weak".

"We hope the Philippines will stop making provocative comments time and time again, and avoid complicating the situation," Liu said.

Contact the writer at zhangyunbi@chinadaily.com.cn