Japan's Prime Minister Shinzo Abe on Monday promised Vietnam six new patrol boats during a visit to the Southeast Asian country, which is locked in a dispute with China over the busy East Vietnam Sea.

Abe's stop in Vietnam completes a tour through an arc of a region where Japan stakes a leadership claim in the face of China's growing dominance and uncertainty over what policy change Donald Trump will bring as U.S. president.

"We will strongly support Vietnam's enhancing its maritime law enforcement capability," Abe said, while emphasizing that the dispute over the East Vietnam Sea should be settled through talks and in accordance with international law.

China claims almost all the East Vietnam Sea, through which about $5 trillion worth of sea-borne trade passes every year. Vietnam and four other countries also say they have rights in the sea, believed to have rich deposits of oil and gas.

Tokyo has no territorial ambitions there, but worries about China's growing military reach into the sea lanes. Japan has a separate dispute with China over a cluster of islets in the East China Sea.

The six new coastguard patrol boats had a total value of 38.5 billion yen ($338 million) and Vietnam would get a concessional loan to pay for them, a Japanese official said. No timeline for delivery has been discussed yet. Japan had previously agreed to provide six old patrol boats to Vietnam.

Maritime security and trade have been themes during Abe's other stops - in Indonesia, the Philippines and Australia.

Given the readiness of the Philippines under President Rodrigo Duterte to move closer to China and further from its traditional U.S. ally, Vietnam is one of fewer regional states showing potential readiness to confront China.

Trump questions

Uncertainty over U.S. policy in Asia was amplified last week by comments from Secretary of State nominee Rex Tillerson that China must stop building islands in the East Vietnam Sea and that its access to those islands must not be allowed.

Despite their differences, Vietnam also maintains a strong diplomatic track with China. China and Vietnam said at the weekend they had agreed to manage their maritime differences and preserve peace and stability.

Both Japan and Vietnam have also been strong supporters of the Trans-Pacific Partnership (TPP) free-trade pact which looks to have stalled in the face of Trump's pledge to withdraw the United States.

In Hanoi, Abe stressed the importance of the TPP and other free trade agreements, but gave no further details.

"Vietnam now plays a more significant role in Japan's foreign policy," said Ha Hoang Hop, a Vietnamese political analyst who has advised the government.

The delegation signed a number of business agreements, including energy and textile projects and a project to help with the impact of climate change. Japan is Vietnam's biggest foreign investor after South Korea.