MANILA/BEIJING: The Philippines’ top diplomat said he and his Vietnamese counterpart discussed Thursday how their governments can work together to deal with territorial disputes with China, including a possible sharing of information to better guard their territories from intrusions.

China said on Thursday it had lodged a formal complaint with the United States after the US Senate passed a resolution expressing concern about Chinese actions in the disputed East and South China Seas.

The US resolution, passed on Monday, listed several examples of worrying Chinese behaviour, including China’s issuing of an official map defining the contested South China Sea as within its national border and of Chinese surveillance ships entering waters disputed with Japan in the East China Sea.

Foreign Secretary Albert del Rosario and Vietnamese Foreign Minister Pham Binh Minh agreed in their meeting in Manila to ask the regional bloc, the Association of Southeast Asian Nations (ASEAN), to seek an early start of negotiations with China on a legally binding accord to prevent an armed conflict from breaking out in the disputed South China Sea. The territorial rifts were high in the agenda of the meeting, which also touched on increasing trade and a possible extradition pact.

Chinese diplomats and those from the 10-member ASEAN have agreed to soon hold consultations on how such a “code of conduct” in the South China Sea should be concluded. Del Rosario said ASEAN should insist negotiations should start immediately after the consultations.

“We want them to take a giant step on China,” del Rosario told reporters after meeting with the Vietnamese delegation. “We decided among ourselves that consultation probably is not enough. We need to talk about negotiations.”

Del Rosario said they also discussed China’s recent offer to jointly develop disputed areas.

He said the Philippines and Vietnam have a similar position of not accepting any joint venture such as oil and gas exploration with China if Beijing insists that it has sovereignty over the areas to be jointly developed.

Many fear the long-unresolved territorial conflicts, which involve the three countries along with Brunei, Malaysia and Taiwan, could spark an armed conflict and disrupt the region’s economic growth.

China has repeatedly urged the United States not to get involved in either dispute.

“The above resolution proposed by a minority of senators took heed of neither history nor facts, unjustifiably blaming China and sending the wrong message,” China’s Foreign Ministry said in a statement.

“China expresses its strong opposition, and has already made stern representations with the US side. We urge the relevant senators to respect the facts and correct their mistakes in order to avoid further complicating the issue and the regional situation,” it added.

Territorial claims by Japan and China over uninhabited islets and the resource-rich waters in the East China Sea, as well as China’s claims over the South China Sea, rank as some of Asia’s biggest security risks.

Chinese President Xi Jinping told his Politburo on Wednesday the country wanted to resolve its maritime territorial disputes peacefully and through talks, but would not compromise on sovereignty and had to step up its defensive capabilities.

Tension over the East China Sea has escalated this year, with China and Japan scrambling fighter jets and ordering patrol ships to shadow each other, raising fear that a miscalculation could lead to a broader clash.

The Philippines and Vietnam have also accused Beijing of becoming more aggressive in their disputes with China in the strategically located and energy-rich South China Sea.