Days prior to the revelation that a new port which could be used by the US Marines was being planned on the edge of Darwin, a placard popped up on one of the city's main commuter arteries.

"No USA war base" blared the letters of the sign hanging off the Bagot Road pedestrian bridge, which neighbours land owned by Australia's Defence Department.

Other similarly slapdash carboard banners were also erected along the street.

Their appearance signalled that some within the tropical capital may have been aware of the impending news — and perhaps the rest of the region's residents shouldn't have been too surprised.

While nothing has yet been declared through official government or Defence channels, the signs of such a development have long existed.

Whether or not the NT will see more foreign boots on the ground, the ADF has been steadily improving and upgrading defence infrastructure in and around Darwin in recent years — a fact which falls somewhat contradictory to the reality that ADF numbers have been on a steady decline in Darwin for the past decade.

Secret planning has begun for a new port facility just outside Darwin which could eventually help US Marines operate more readily in the Indo-Pacific.

Precise details remain tightly guarded but senior defence and federal government figures concede the proposal may risk angering China even though it's a commercial port, not a new military base.

Multiple officials, speaking on the condition of anonymity, have confirmed to the ABC the multi-use development would be in the Glyde Point area, roughly 40 kilometres north-east of Darwin's existing port.

Darwin port, which was controversially leased to a Chinese company in 2015, has existing defence facilities such as a multi-user barge ramp, but the new proposed facility would have the additional advantages of being less busy and less visible.

If approved, the new port could eventually be able to accommodate large amphibious warships such as Australia's Landing Helicopter Docks, and American vessels such as the USS Wasp, which recently arrived in Sydney.

Strategic experts believe a new deep-water port would be ideally suited for the more than 2,000 US Marines and their equipment during regular rotations through the Top End.

"The Americans are clearly not withdrawing from the Indo-Pacific, whether it's because of their strategic competition with China or more generally," said Rory Medcalf from the Australian National University.

It's understood a formal announcement on the new maritime facility could be made as early as next month when the "Talisman Sabre" war games with the US begin in the Northern Territory and Queensland.

A U.S. warship struck by a container vessel in Japanese waters failed to respond to warning signals or take evasive action before a collision that killed seven of its crew, according to a report of the incident by the Philippine cargo ship's captain.

Multiple U.S. and Japanese investigations are under way into how the guided missile destroyer USS Fitzgerald and the much larger ACX Crystal container ship collided in clear weather south of Tokyo Bay in the early hours of June 17.

In the first detailed account from one of those directly involved, the cargo ship's captain said the ACX Crystal had signaled with flashing lights after the Fitzgerald "suddenly" steamed on to a course to cross its path.

The container ship steered hard to starboard (right) to avoid the warship, but hit the Fitzgerald 10 minutes later at 1:30 a.m., according to a copy of Captain Ronald Advincula's report to Japanese ship owner Dainichi Investment Corporation that was seen by Reuters.

The collision tore a gash below the Fitzgerald's waterline, killing seven sailors in what was the greatest loss of life on a U.S. Navy vessel since the USS Cole was bombed in Yemen's Aden harbor in 2000.

Those who died were in their berthing compartments, while the Fitzgerald's commander was injured in his cabin, suggesting that no alarm warning of an imminent collision was sounded.

A spokesman for the U.S. Navy's Seventh Fleet in Yokosuka, the Fitzgerald's home port, said he was unable to comment on an ongoing investigation.

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.

US warships could soon become a more familiar sight in Darwin Harbour.

US Senate armed services committee chair John McCain has put a stronger US and Australian naval presence to the north of Australia firmly on his agenda during his coming visit to Australia.

Darwin and Perth have traditionally been ports of call for US warships when operating in the Pacific.

Senator McCain, who will meet with Prime Minister Malcolm Turnbull, will lay on the table the strategy behind Donald Trump’s Asia-Pacific plan to combat China’s behaviour in the South China Sea and how a heavier US and Australian naval presence in the region would achieve “peace through strength” in the region.

He said the US was developing strategies for the Asia-Pacific region which he thought would have a lot to do with future strategic co-operation with Australia.

“I think Australia could play a key role, particularly since we are witnessing a very large investment in an expanded US navy in the decade ahead,” Mr McCain said.

Mr McCain’s comments on an increase in naval forces in the region comes at the same time the US has beefed up its military strength in Darwin. The US has just sent to Darwin the sixth and most complex US marine air ground task force to be deployed to the Territory. Along with 1250 battle ready marines it has a large aviation combat element.