The United States and China both wanting to engage Asean in separate maritime exercises shows that they recognise its geopolitical importance, said analysts.
But one tricky issue remains about the location of the Asean-US Maritime Exercise, scheduled to take place next year.
The exercise was announced after the 12th Asean Defence Ministers' Meeting (ADMM) at the Shangri-La Hotel yesterday.
The Asean-China Maritime Field Training Exercise will be held in Zhanjiang, China, from Monday to Oct 28.
Asean defence ministers held separate informal meetings with US Defence Secretary James Mattis and Chinese Defence Minister Wei Fenghe after the ADMM.
When asked about the location of the Asean-US exercise at a media conference yesterday, Defence Minister Ng Eng Hen, who chaired the ADMM, said it has yet to be decided.
He said the exercises with China and the US are a positive development, and that Asean would be open to other exercises too.
"What does it signify? I think it shows that Asean wants to engage Plus partners if it is within the right spirit and that it would build confidence and cooperation."
He added that the US and China had proposed their respective exercises with Asean.
Maritime specialist Collin Koh of the S. Rajaratnam School of International Studies said China and the US have long recognised the geopolitically strategic position of South-east Asia.
He believes the Asean-US exercise will be held in a "non-sensitive" location to ensure full participation.
"The scope (of the exercise) may still be tied more to less-sensitive topics such as humanitarian and emergency response and maritime safety because we still need to take into account the wide disparities in capabilities between the Asean navies, which means having to cater to the lowest common denominator," he said.
International Institute for Strategic Studies senior fellow William Choong said Asean played its cards well by letting the US in on an exercise at the same time it does with China. "Because otherwise, there will be talk about whether Asean is getting closer to China at the expense of the US."
A Ministry of Defence statement yesterday said Mr Mattis and Dr Ng welcomed the Asean-US exercise as a useful confidence-building measure that would enhance cooperation between regional navies.
At the meeting between Asean ministers and General Wei, the Chinese minister proposed three new areas to deepen China's defence engagement with Asean: Establishing an Asean-China direct communications hotline, having think-tank exchanges and a young leaders' exchange programme.