The war of words between China and the Philippines over disputed islands in the South China Sea escalated on Tuesday, ahead of a key regional security dialogue in Indonesia.

China's embassy in the Philippines warned that plans by five Filipino lawmakers to visit the disputed Spratly archipelago -- in what Manila calls the the West Philippine Sea -- could damage bilateral ties.

"It... serves no purpose but to undermine peace and stability in the region and sabotage the China-Philippines relationship," the embassy said of the one-day trip scheduled for Wednesday.

Philippine Foreign Secretary Alberto del Rosario, speaking after meeting his Southeast Asian counterparts in Bali, said meanwhile that Manila planned to seek UN arbitration of its conflicting claims with China.

China had rejected arbitration by the International Tribunal for the Law of the Sea, he said, so Manila had to "look at other dispute settlement mechanisms" such as the UN Convention on the Law of the Sea.

Indonesian President Susilo Bambang Yudhoyono expressed frustration that drawn-out talks over a code of conduct in the resource-rich sea were making little progress, ahead of the region's main security dialogue on Saturday which will be attended by US Secretary of State Hillary Clinton and others.

"We need to finalise those long overdue guidelines because we need to get moving to the next phase," Yudhoyono said in a keynote speech to the meeting of Association of Southeast Asian (ASEAN) foreign ministers in Bali.

"We need to send a strong signal to the world that the future of the South China Sea is a predictable, manageable and optimistic one."

The Indonesian leader noted that it took ASEAN and China 10 years to agree on a declaration for a code of conduct, and they have been discussing the guidelines to implement the code for another nine years without agreement.

"Things do not necessarily have to be this slow," Yudhoyono said.

China, the Philippines, Vietnam, Brunei, Malaysia and Taiwan have overlapping claims to parts of the South China Sea including the Spratlys.

The area is believed to be rich in oil and gas and is a crucial route for global shipping trade. The United States has defence pacts with Taiwan and the Philippines and claims a "national interest" in the free movement of shipping.

The tensions are set to overshadow five days of meetings in Bali culminating Saturday in the ASEAN Regional Forum security dialogue, which brings in China, Japan and the United States.

ASEAN Secretary General Surin Pitsuwan said Asian countries had to "send the right signal to the world" that they can deal with sensitive territorial disputes and not just trade.

Frictions have intensified lately, with the Philippines and Vietnam protesting over what they say are increasingly forceful Chinese actions in the area.

Recent incidents include Chinese forces allegedly opening fire on Filipino fishermen, shadowing an oil exploration vessel employed by a Philippine firm and putting up structures in areas claimed by the Philippines.

Vietnam voiced anger after a Chinese vessel cut the exploration cables of a Vietnamese survey ship in May, and Beijing condemned US-Vietnam naval exercises that began last week off Vietnam's coast.

China staged its own military exercises in the South China Sea in June and announced plans to boost its offshore maritime patrol force.

Not to be left out, Taiwan has said it is considering deploying missile boats in the waters and tanks on disputed islands.

China wants to negotiate bilaterally with individual ASEAN claimants, while ASEAN wants to deal with China as a group.

Clinton and Chinese Foreign Minister Yang Jiechi will arrive in Bali later this week ahead of the ASEAN Regional Forum.