Australia would be invited to join the United States, Japan and South Korea in war-game drills shooting down North Korean missiles under a push by the US Congress.

A bill put forward by a leading Congressional Republican earmarks money for joint-exercises between the four countries for ballistic missile defence next year.

Significantly, it groups Australia with the countries at the forefront of the North Korean nuclear threat. Also, it signals an expectation in Washington that US allies play a greater role in countering regional dangers, defence experts said.

North Korea has provoked increasing alarm in capitals across the Asia-Pacific in recent weeks by repeatedly testing ballistic missiles in the hope of being able to deliver nuclear warheads across oceans.

North Korea fires what appears to be a short-range ballistic missile.

It has threatened Australia with a nuclear weapons strike if it continued to "blindly" follow the US.

How to tackle the rogue regime is expected to be a major focus of this weekend's Shangri-La Dialogue in Singapore at which Prime Minister Malcolm Turnbull will deliver the keynote speech and at which US Defence Secretary James Mattis will also give a much-anticipated speech laying out US pledges and expectations for Asia.

The Asia-Pacific defence spending bill put forward by House Armed Services Committee chairman Mac Thornberry - which will help shape Pentagon policy over the next year - includes $15 million for "joint and other exercises with the armed forces of the governments of Japan, South Korea, Australia and the United States for the defence against and defeat of ballistic missile forces of North Korea".

Fairfax Media understands Australia has not received any invitation yet for involvement in such exercises. Defence Minister Marise Payne said Australia "supports very clear messages to North Korea that it should not continue down this path of risking regional and global security" and reiterated calls for China to play a more forceful role.

Australia has previously taken part in Nimble Titan, a classroom-based missile defence exercise involving a large number of countries.

The exercises flagged by Congress would be more substantial and more narrowly focused on key countries, though experts stressed the amount of money Congress was considering would allow only for limited live drills or so-called "table top" exercises - simulations that test decision-making.

Military expert Malcolm Davis, from the Australian Strategic Policy Institute (ASPI), said the Pine Gap facility could be used to track missiles but Australia needed to upgrade its three new Air Warfare Destroyers for missile defence.

The destroyers, which will start to be commissioned from later this year, have the radar systems to track missiles but not the capability to shoot them down.

"It's very clear that the Americans want Australia to become more directly involved in missile defence work," Dr Davis said.

"For years we've talked about missile defence but we've never done much about it ??? I think the Americans are sending us a message saying you are going to need to do more than just talk about missile defence."

His colleague, ASPI executive director Peter Jennings, said such exercises would "make sense in the current strategic environment where the threat from missiles is growing".

John Blackburn, a former deputy chief of the airforce who wrote a recent paper on missile defence for the Williams Foundation think tank, said such joint exercises would be a "logical next step" to developing a regional missile defence network.

"The exercises are great because by working with these countries, we learn what's involved and just how hard it is."

He said it needed to be a regional "team sport" because a network of ships, missiles and radars could much more reliably stop ballistic missiles than one country alone.

"If we wait to react, we're buggered," he said.

Ben Schreer, head of the department of security studies and criminology at Macquarie University, said the US seemed to expect more from Australia in the region.

US Secretary Mattis would be watched closely this weekend in Singapore for whether the US would indicate a "much stronger US presence and posture for the Asia-Pacific region" - a successor to the Obama-era "pivot" to Asia.

If so, "he will say allies need to front up more and that will include Australia", Professor Schreer said.

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