Ishiba made the pledge during a visit to Jakarta, where he held talks with President Prabowo Subianto on a range of bilateral issues.

"We agreed on establishing working-level defense consultations on our maritime security, including on defense equipment technical cooperation," Ishiba was quoted as saying in a joint statement. 

"We also agreed to [...] provide high-speed patrol boats through Official Security Assistance, which would be our first with Indonesia."  

He said the two countries also agreed to cooperate in decarbonized energy sectors, such as geothermal power, hydrogen, ammonia and biofuels. 

Before arriving in Jakarta, Ishiba held talks in Kuala Lumpur with Malaysian Prime Minister Anwar Ibrahim, describing strengthening ties with Southeast Asia as "one of the biggest priorities" for Japan.  

The trip, he said, made him aware of the "explosive growth of the two countries" and reaffirmed his view that Japan and key ally the United States must further engage the Southeast Asian nations.

"Diplomatic engagement in this region is as extremely important to Japan as it is to the United States", Ishiba said. 

"I would like to share the understanding with [...] Trump that Japan and the US working together towards the peace and stability of this region will contribute significantly to the peace and stability of the Indo-Pacific region and the whole world," he continued referring to US president-elect Donald Trump.

With US encouragement as it seeks to counter China, Japan has been deepening security ties in the region. 

China claims almost all of the South China Sea despite an international ruling in 2016 concluding its claims have no legal basis. Huge unexploited oil and gas deposits are believed to lie under the South China Sea, though estimates vary greatly.

Last month, Japan's top diplomat Takeshi Iwaya expressed "serious concerns" to his Chinese counterpart over Beijing's increasing military activity, and also cited worries over the "East China Sea situation, including around the Senkaku Islands", a chain of uninhabited islands claimed by Beijing but administered by Tokyo.

Japan is already providing equipment and other assistance to the Philippines, which is also engaged in territorial disputes with China. 

Last year the Philippines ratified a key defense pact with Japan, which allows them to deploy troops on each other's soil. 

His trips to Malaysia and Indonesia mark Ishiba's first official state visit since taking office in October.