The US Marine Corps may ground its entire air fleet for a safety review following the crash of an Osprey tilt-rotor aircraft in Australia that killed three Marines, a defense official said Monday.

The Japan-based Marine MV-22 Osprey crashed Saturday during an exercise off the Australian coast, leaving three service members missing and presumed dead.

"We are looking at our options in terms of reviewing safety across the Marine Corps fleet at the moment ... pending an across-the-board safety review," a US defense official told AFP, noting that the grounding could affect all flying squads in the service.

US officials are also weighing a request by Japan's new defense minister, who told the US military on Monday of his "many concerns" after it flew an Osprey in Japan following the crash.

Itsunori Onodera, appointed Thursday as Japan's defense minister, asked the US to temporarily stop flying the aircraft in his country following the accident.

According to the US official, the Osprey crashed after clipping the back of the USS Green Bay while trying to land on the amphibious transport ship. The Okinawa-based aircraft which crashed was in Australia as part of a joint military exercise called Talisman Sabre, which has just ended in Queensland state.

On Thursday, the USS Bonhomme Richard made its way toward Sydney as Australian and US forces commenced their Talisman Saber exercise, the seventh of the large biennial training drills.

According to a Navy statement, more than 33,000 service members from the US and Australia will participate in "high-end warfighting scenarios” designed to “innovatively prepare for regional and global security challenges."

The statement adds that Talisman Saber, jointly sponsored by the US Pacific Command and the Australian Defence Force Headquarters Joint Operations Command, will be mostly sea and land based. It will take place in and around Australia and include “live and virtual training exercises” and amphibious landings.

More than 200 aircraft will be participating, including advanced F-35B Lightning II stealth fighters and tilt-rotor Ospreys, along with 21 ships including the Bonhomme Richard Expeditionary Strike Group and the USS Ronald Reagan aircraft carrier.

"Exercises like Talisman Saber are precisely where we really learn how to take advantage of cutting-edge technology to outpace our adversaries," Adm. Harry Harris, head of US Pacific Command, said in a US Navy statement saying.

During the exercise’s opening ceremony, Harris said he challenged all branches of the US armed forces to "find new ways to enable our joint and multinational combined forces to be faster, more precise, more cost-effective and most importantly, more lethal."

Speaking of Talisman Saber’s symbolic value, Harris told reporters, "I’m pleased about that message it sends to our friends, allies, partners and potential adversaries … I think this demonstrates the importance of alliances in general and the value of this alliance in particular." On Wednesday, the commander made his third trip to Australia in roughly half a year, telling an audience at Brisbane’s Australian Strategic Policy Institute that Washington takes its relationship with Australia seriously, and that the alliance between the two countries could help stop the spread of jihadist extremist groups. Australia is a global leader in the fight against Daesh, he pointed out.

Lieutenant Colonel Brian S. Middleton, says the 1250 US Marine deployment to Darwin stands ready to fight if tensions between his country and North Korea escalate into direct conflict.

Lieut. Colonel Middleton said when US Marines were in forward deployment they were ready for battle.

Lieut. Colonel Middleton is leading the sixth and most complex US marine air-ground task force to be deployed to the Territory.

Along with the 1250 marines that make up the latest Darwin rotation of US troops, it will eventually include up to 13 aircraft, four tilt-rotor Ospreys, five Super Cobra helicopters and four Huey helicopters.

When asked about the North Korea stand-off he said: “We stand ready to fight.”

The marines are from 3rd Battalion, 4th Marine Regiment from Camp Pendleton, California. They will be based at Robertson Barracks, RAAF Base Darwin and Defence Establishment Berrimah.

Marine Rotational Force Darwin is mainly a series of joint exercises, training and exchanges between the US and the Australian Defence Force, but some exercises will also involve military personnel from China and other Asian countries.

The US has rotated a small force of Marines through Darwin since 2012. It was originally planned to send a full Marine Air-Ground Task Force of 2500 Marines to Australia by 2016, but the timeline has been pushed back to around 2020.

More than 1,000 US marines begin arriving in the Top End and say they are ready for whatever may happen as North Korea escalates its nuclear threat.

The first group of 1,250 marines touched down in Darwin on Tuesday morning for their sixth annual dry season rotation in the Top End.

Their arrival comes as Foreign Minister Julie Bishop defended US President Donald Trump's "they gotta behave" message to North Korean leadership after its failed missile test on Sunday.

"[North Korea] is on a path to achieving nuclear weapons capability and we believe Kim Jong-un has a clear ambition to develop an intercontinental ballistic missile capable of carrying a nuclear payload as far as the US," Ms Bishop said.

"That would mean Australia would be in reach so unless it is prevented from doing so, it will be a serious threat to the peace and stability of our region, and that is unacceptable."

In Darwin, the rotation's commanding officer Lieutenant Colonel Brian Middleton said the force was ready, come what may.

"Any time a marine force is forward deployed, we are always on standby for anything," he said.
He said this year's contingent was "the most robust package" the marines had put together for training in the Top End, featuring an "ace aviation combat element" of 13 aircraft.

Over the next two weeks, the deployment's largest fleet of military aircraft yet will be brought to Australia as part of the agreement, including four high-speed troop transporters, the MV-22 Osprey, five Super Cobra helicopters and four Huey helicopters. The next six months will see the troops train with their Australian counterparts and other nations, including Japan and China.

As a parade of senior Australian and United States commanders and their public affairs teams attempted to stay on message about the “humanitarian” aspects of the biggest military exercise ever in Australia — the shadow of China was cast over every facet of the intensive war gaming.

During a lightning visit to the exercise area on Sunday, Prime Minister Tony Abbott insisted that China appreciated that Australia was an ally of the United States.

Mr Abbott further confused things when he declined to rule out the possible future permanent basing of USA forces in Northern Australia.

The Marine Corps training rotation is scheduled to grow from 1100 now to 2200 in the next few years, but Mr Abbott left the door open for even greater access for USA forces to the deserted and wide-open training ranges of Northern Australia.

When asked specifically if there would be USA forces based in the north the prime minister was noncommittal.

“Let’s see what the future holds. I am not saying there will be more … but they shouldn’t shock or surprise anyone.”

Ask any of the thousands of USA Marines participating in Talisman Sabre — particularly those based on the tiny island of Okinawa in Japan — and they will tell you that the NT and Rockhampton are war games nirvana.