Singapore's upcoming advanced multi-role combat vessels will be operational by 2027, navy chief Lew Chuen Hong said.

These "motherships" capable of deploying unmanned systems are meant to replace the current fleet of missile corvettes, first commissioned in 1990, by 2030.

Said Rear-Admiral Lew: "We are now going through the detailed procedures to make sure that we plan and design her right, and we aim to have the first ship by the end of 2025, and to see her operational (by) 2027."

He gave the update during an interview ahead of the Navy@Vivo public outreach event at VivoCity mall that starts today.

RADM Lew also said the Invincible-class submarine launched earlier this year is currently undergoing harbour trials in Germany. It is scheduled to return to Singapore by 2021.

Asked about future editions of the Asean-China and Asean-US maritime exercises, he said these are being discussed but there are no specific details fixed yet.

RADM Lew stressed the importance of Asean centrality and said that Asean countries see value in engaging all partners, including the US and China.

"The common interest of Asean is for continued peace and stability in this region," he said.

"And, really, it is not in our collective interest to pick sides or to see a flare-up of tensions and conflicts."