Japan and Indonesia are strengthening their security ties through measures such as expediting talks on the export of Japanese defence technology and by having their defence and foreign ministers meet soon.
This reflects concerns over growing Chinese regional assertiveness, and comes as Japanese Prime Minister Yoshihide Suga met Indonesian President Joko Widodo at the Presidential Palace in Bogor, south of Jakarta, yesterday.
Mr Suga, who is the first foreign leader to visit Indonesia since the Covid-19 pandemic, was greeted with a 19-gun salute.
He flew in from Vietnam, and Japanese diplomats said the four-day, two-nation trip was meant to symbolise Japan's continued commitment to and support for Asean.
Regarded as a greenhorn when it comes to foreign affairs, Mr Suga is following in the footsteps of his predecessor Shinzo Abe, who also visited Vietnam and Indonesia first after he became prime minister in December 2012.
A key priority for Mr Suga is to cement Asean's backing for Japan's Free and Open Indo-Pacific vision, which he stressed is aligned with the Asean Outlook on the Indo-Pacific pioneered by Indonesia.
The Asean initiative is built on principles such as transparency and respect for international law, with the bloc "being an honest broker within the strategic environment of competing interests".
Mr Suga told a news conference, with Mr Joko beside him, that their defence and foreign ministers will meet in the near future under the so-called two-plus-two framework.
This will be the first meeting between the ministers since 2015, and Indonesia is the only Asean nation with which Japan has a two-plus-two arrangement.
Mr Joko said that closer cooperation between Japan and Indonesia was critical amid the "increasingly sharp rivalries between the world's great powers", alluding to the intensifying clash between the United States and China.
But he added that he hoped the South China Sea will "continue to be peaceful and stable".
A day earlier, in Hanoi, Mr Suga agreed in principle to a military equipment and technology export pact with his Vietnamese counterpart Nguyen Xuan Phuc.
Vietnam is one of the claimants in territorial disputes over the South China Sea. Although Indonesia is not a claimant state in the dispute, its exclusive economic zone overlaps with China's "nine-dash line" blanket claim over large swathes of the waterway.
Japan is also encouraging its companies to diversify their supply chains so as to reduce their reliance on China, with the risk of concentrating factories in a single market having been made evident by the Covid-19 outbreak.
Mr Joko said he appreciated the investments made by Japan, which is regarded in Indonesian circles as a strategic economic partner.
Mr Suga vowed to promote cooperation in infrastructure projects, such as mass rapid transit, the Jakarta-Surabaya semi-fast train, the construction of the Patimban port, as well as working together to increase economic resilience.
He also committed 50 billion yen (S$642.44 million) in long-term, low-interest loans to Indonesia to help it cope with the economic fallout from the Covid-19 pandemic.
Indonesia has been the worst hit in South-east Asia, with more than 360,000 confirmed cases and more than 12,000 deaths.
The loan amount is on top of an earlier 50 billion yen, pledged through the Japan International Cooperation Agency in August.
The Japanese and Indonesian leaders also agreed to begin talks on a travel corridor for business travellers, as well as to resume travel for nurses and care worker trainees.
Mr Suga returns to Tokyo today.
• Additional reporting by Arlina Arshad