Australian warship HMAS Parramatta sailed with guided missile-cruiser USS Bunker Hill and then rendezvoused with amphibious assault ship USS America and guided missile destroyer USS Barry.

The operations began on April 13 and come as China continues to expand its presence in the region, including opening research stations on artificial reefs in territory claimed by the Philippines and other nations.

"We look forward to every opportunity we get to work with our stalwart Australian allies at sea," Rear Admiral Fred Kacher, commander of the America Expeditionary Strike Group, said on the US Navy's website.

"To bring this much combat capability together here in the South China Sea truly signals to our allies and partners in the region that we are deeply committed to a free and open Indo-Pacific."

The HMAS Parramatta and its US counterparts took part in live fire exercises, co-ordinated helicopter operations, small boat force protection drills, command and control integration and maneuvering interoperability.

More than 3000 US sailors and marines watched or participated in the exercise.

"They (Australia) have the same interest in ensuring freedom of navigation and observance of internationally accepted norms and customs pertaining to the law of the sea," Captain Kurt Sellerberg, commanding officer of the USS Bunker Hill, said.

"The Aussies are true professionals in every sense of the word, and our current combined deployment exemplifies a shared commitment to our historically strong and enduring relationship."

Australian Associated Press