State-of-the-art US missile destroyers will join ageing Philippine warships for naval exercises this week in a timely show of unity as tensions with China escalate over a maritime dispute.

The 11 days of exercises start on Tuesday off the southwest Philippine island of Palawan in the Sulu Sea, close to the disputed waters of the South China Sea where Manila has complained of increasing Chinese provocation.

Officially the training is an annual event not linked to the territorial row, but it nevertheless offers the Philippines comfort shortly after appealing to its longtime ally and former colonial power for help in containing China.

"The exercises show that the Philippines and the US are still very close. They (Philippine leaders) hope that the Chinese will be impressed by this," said Ben Lim, a political science professor at Ateneo de Manila University.

"It will give the Philippines confidence in regard to diplomatic leverage. When they meet the Chinese again in peaceful negotiations, they can say 'the Americans are on our side'."

The Philippines has in recent months complained of allegedly increasingly aggressive actions by China in waters claimed by both nations in the strategically vital and potentially resource-rich South China Sea.

The Philippines and China -- along with Brunei, Malaysia, Taiwan and Vietnam -- claim all or part of the South China Sea, and the area has long been considered one of Asia's potential military flashpoints.

Philippine President Benigno Aquino this month accused China of inciting at least seven incidents recently, including one in which a Chinese vessel allegedly opened fire on Filipino fishermen.

He accused China of breaking international law by intruding within the Philippines' 200-nautical-mile economic exclusion zone, and called on the United States for help in defending his country's claims against the Chinese.

Foreign Secretary Albert del Rosario last week travelled to Washington, where he won some backing from the United States as the superpower offered to help modernise the cash-strapped Philippine military.

"We are determined and committed to supporting the defence of the Philippines," US Secretary of State Hillary Clinton told a joint news conference with del Rosario.

No specifics were immediately announced but del Rosario later said that US authorities had vowed to help boost the Philippines' intelligence capabilities in the South China Sea.

Nevertheless, both nations have emphasised that the naval exercises starting Tuesday -- named Cooperation Afloat Readiness and Training (CARAT) -- are part of long-term US efforts help the Philippine military.

"The US and Philippine navies have a long history of working together, and exercises like (these) provide a great venue for us to hone our skills and increase our interoperability," US CARAT commander Captain David Welch said.

The United States will send 800 sailors and two guided missile destroyers, plus a diving and salvage ship, to the 17th staging of the exercises, the US military said in a press release.

Highlighting the disparity between the allies' military capabilities, the Philippine navy said it would deploy two World War II-vintage vessels armed only with cannon for CARAT.

About 300 Philippine sailors will take part, according to navy spokesman Lieutenant Noel Cadigal.

The United States is scheduled to stage similar exercises with Vietnam next month, although it has insisted they too have nothing to do with South China Sea tensions.

Vietnam has made accusations similar to those of the Philippines over alleged Chinese actions in the South China Sea recently.

Amid the spike in tensions, China has repeatedly said it wants to solve the territorial disputes peacefully while warning the United States it has no role to play in the spats.