CANBERRA, Australia--A top U.S. Marine Pacific commander has urged close ally Australia to consider taking on a more visible regional policing role, saying he would like the country to deploy large new amphibious warships into the South and East China Seas in future to help allay security uncertainty caused by a more assertive China.

Following recent clashes between China and regional neighbors including Japan, the Philippines and Vietnam in the East and South China Sea, the deputy commander of the Marines in the Pacific said U.S. allies and friends in the region were anxious to maintain a security "status quo" in Asia.

"It is a bad word, but it is very applicable, I think," Major-General Richard L. Simcock said in an interview on the sidelines of a summit on American ties with Australia. Canberra is currently strengthening its alliance with Washington and in past years has tried to play a role as America's regional "deputy sheriff".

"Status quo represents the security, the economic benefits, that have come to the Asia-Pacific region over the last 70 years. There's an apprehension to drastic change," Maj-Gen Simcock said.

Washington and Canberra have criticized Beijing recently for what they view as strong-arm tactics in spats with other countries in the region--including Japan--over contested islands in the South and East China Seas. China has also irked Hanoi by deploying an oil-drilling platform in disputed waters close to Vietnam.

Following talks in the U.S. last week between President Barack Obama and Australia's Prime Minister Tony Abbott, a White House statement said both countries were looking at fitting new Australian navy destroyers with missiles capable of shooting down ballistic missiles used by North Korea and China.

Australia is also building two large amphibious assault carriers weighing 27,000 tons as part of a military buildup worth US$85 billion over a decade and buying new submarines, stealth fighters and a larger army. The ships, the first of which is due in service next year, are the size of small aircraft carriers and will be able to carry more than 1,000 troops, as well as tanks, helicopters and aircraft. The country's Defense Minister David Johnston has said the two carriers may also carry marine versions of F-35 fighter aircraft.

Canberra is also backing Japan's aim to remove postwar curbs on military roles beyond self-defense and consider supporting other Asian nations to counter China's muscle flexing, with military officials from both countries to hold talks on security with U.S. representatives in coming months. Both countries are also looking at sharing submarine technology.

In Australia's case, Prime Minister Tony Abbott's Conservative government says the build up is needed to protect billions of dollars worth of oil and gas assets off the country's remote northwest coast which will likely see the country vie with Qatar to be the world's top LNG exporter.

American energy company Chevron Corp's Australian unit managing director Roy Krzywosinski said on Wednesday that the company was well aware its flagship $54 billion Gorgon liquefied natural gas project and others under development off Australia's remote northwest coast could be considered "strategic targets", along with their produce and the routes and paths they took to customers'.

Maj-Gen Simcock said on Wednesday that he would like Australia in particular to taper its past reluctance to sending ships north of neighboring Indonesia on regular patrols, if only to be available to help with humanitarian disasters.

"Absolutely (we want that)," he said. "The Asia-Pacific region is too big for any one country, so when countries develop this amphibious capability that they want, and they are asking us to help them develop it, it is a win-win for all concerned. It allows them to address numerous issues."

The U.S., he said, wanted to help both Japan and Australia develop an amphibious assault and movement capability in Asia as it offered inherent flexibility in both defense and aid provision.

Australia's Foreign Minister Julie Bishop said earlier in a speech to the conference that it was vital the U.S. remained "engaged and connected" with the Asia region as part of Mr. Obama's promised economic, strategic and diplomatic pivot to Asia, first outlined in Australia in 2011.

China's role in challenging U.S. pre-eminence should be, she said, as a prosperous nation "actively and constructively engaged as a significant power in regional and global affairs'.

In 2011, the U.S. and Australia reached a deal to rotate a 2,500-strong U.S. marine expeditionary brigade through the northern Australian city of Darwin for several months a year as part of Washington's "pivot". The long-standing allies have been united in criticizing what U.S. Defense Secretary Chuck Hagel recently called "destabilizing, unilateral actions" by China in relation to its neighbors.

Australia's Defence Minister, Mr. Johnston, speaking at the same conference, said Canberra didn't take a position on competing South and East China Seas claims, but had "a legitimate interest in the maintenance of peace and stability, respect for international law, unimpeded trade and freedom of navigation".

"Australia cannot be secure in an insecure region," he said. "We share the serious concerns expressed by Asean over recent territorial tensions in the South China Sea and urge all parties to exercise restraint, refrain from actions that could increase tensions, and to clarify and pursue claims in accordance with international law."

A spokesman for Mr. Johnston declined to respond directly to Maj-Gen Simcock's comments.

Write to Rob Taylor at rob.taylor@wsj.com

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