United States Secretary of Defense Lloyd Austin III said China's harassment of Filipino sailors in the West Philippine Sea is "irresponsible behavior".

Austin made his statement in a joint press conference with his Australia, Japan and Philippine counterparts in Honolulu days after the Chinese Coast Guard damaged Philippine government vessels conducting humanitarian mission and maritime patrol in the vicinity of Scarborough Shoal.

Austin was joined by Japanese Minister of Defense Kihara Minoru, Defense Secretary Gilberto Teodoro Jr. and Australian Deputy Prime Minister Richard Marles during the meeting.

"We've been very clear to everyone, to include Beijing, that kind of behavior that we've seen, where Filipino crews are put in danger, where sailors have been injured and property damaged, that's irresponsible behavior and it disregards international law," he said.

"I would just say that you've heard me say, you've heard our President say a number of times that our commitment to the treaty is ironclad and we stand with the Philippines. And finally, let me just say that as all of us have said, we're doing historic work with the Philippines and helping them modernise their military. And it's exciting work and we look forward to continuing to make progress," he added.

Austin said the defense ministers of four countries met in Hawaii for the first time to share their common vision to maintain the freedom of navigation in the Indo-Pacific region.

"We've gathered here because we share a vision for peace, stability and deterrence in the Indo?Pacific. We've charted an ambitious course to advance that vision together and that's why today's meetings were so important," he said.

"We're here today because we share a common vision and that vision is a free and open Indo?Pacific. And we believe that our continued work together, and we’ll continue to promote activities that will help lead to the accomplishment of that vision," he added. Robina Asido/DMS