HANOI -- Vietnamese President Tran Dai Quang on Friday called for Japan's active involvement in helping to resolve his country's territorial dispute with China in the South China Sea.

Speaking to The Nikkei ahead of his first visit to Japan from next Tuesday to June 2, Quang used stronger-than-usual language, apparently aiming to send a warning to China, which has been increasing its military presence in the region by conducting bomber drills and deploying missiles.

The president, Vietnam's second most powerful man after the Communist Party secretary general, said Japan can contribute greatly in maintaining peace in Asia, including helping to resolve tensions in the South China Sea and denuclearize North Korea. Coordinated action between Japan and his country will be necessary, he said.

Vietnamese leaders have generally tended to use softer expressions in referring to the South China Sea, so as not to arouse China. Quang's departure from that tendency may reflect a heightened concern in Vietnam after a series of moves in May by China in nearby waters, including drills by bombers in the Paracel Islands area and deployment of cruise missiles in the Spratly Islands.

Japan has increased its involvement in the region. Its Maritime Self-Defense Force vessels make regular visits to strategically important Danang Bay and Cam Ranh Bay.

Quang also asserted the need to establish a legally binding code of conduct based on international law.

The president praised Vietnam and Japan's contributions to the signing of the Trans-Pacific Partnership in March by the remaining 11 member countries, including Japan and Vietnam. He also said he will continue to make efforts to encourage the U.S. and other countries to join the TPP.

This was clearly a reference to U.S. President Donald Trump, who withdrew his country from the trade pact but has hinted that he wants to restart talks. Attention is focused on whether the U.S., which was Vietnam's biggest export destination in 2017, will return to the negotiating table.

Quang also said he expects Japan will help Vietnam improve the quality of his country's infrastructure. Vietnam, which faces financial difficulties, plans to use private funds, derived from such sources as public-private partnerships and build-operate-transfer schemes. The country hopes Japanese companies will enter these areas.