Papua New Guinea (PNG) will join Australia's national rugby league competition, after signing a deal that obligates them to shun security ties with China.

The Pacific nation has produced many stars of Australia's National Rugby League (NRL) and has long been lobbying to join the franchise.

Australia will provide A$600m (£301m, $384m) over ten years to set up the team – which will be based in Port Moresby and compete from 2028 – and help develop the game at a grassroots level across the Pacific region.

In exchange, PNG signed a separate pact which it says reaffirms its commitment to Australia as its major security partner.

The precise terms of the dual deals are confidential, but the BBC understands they allow Australia to withdraw funding if PNG enters a security agreement with a nation outside the so-called "Pacific family". That term is widely accepted to exclude China, despite Beijing's efforts to gain a foothold in the region.

If Canberra pulls out, the NRL is then obligated to drop the PNG team.

Announcing the agreement in Sydney on Thursday, PNG Prime Minister James Marape said it was a "monumental" opportunity for his country, and one aimed at fostering "unity" - not only between the 830 language groups in PNG, but also between the nation at large and its closest neighbour.

"For us, it's not just sport and sport commerce, it is [about]... uniting the most diverse nation on the face of planet Earth and also uniting PNG-Australia together in ways that matter most, people to people," he told reporters.

Australian Prime Minister Anthony Albanese declared it was a "great day" for both countries, and said PNG - the only country in the world where rugby league is the national sport - "deserves" a spot in the league.

"The new team will belong to the people of Papua New Guinea… And I know it will have millions of proud fans barracking for it from day one," Albanese said.

It is a big milestone for the NRL too. This is the first time the competition, which is trying to lure international audiences, has expanded overseas. The only other foreign team, the New Zealand Warriors, has been a part of the competition since its inception almost three decades ago.

NRL boss Peter V'landys had been championing the PNG bid, arguing it was a huge opportunity for the league, as well as for PNG's economic development.

A name and uniform for the new team will be decided at a later point.

Stuart Murray, an Associate Professor of International Relations, told the BBC that while Australia's use of sport as a diplomatic strategy is nothing new, this agreement is unprecedented.

The country has over the past decade been "thinking innovatively about how you can marry sport with policy to counter classical security threats" said Dr Murray, from Bond University.

In this case, he added, "the scale, the size, the scope and the funding, and the fact that it's being endorsed at such a high level with both prime ministers - that's never been done before".

"Basically, through this one channel, we will open up 20 or 30 other channels - for business, trade, policing, educational exchange, gender work, climate change... I think it is fantastic."

Australia and China have each been vying for greater influence in the Pacific in recent years. After Beijing inked a major policing deal with the Solomon Islands in 2022, Australia has spent years trying to forge exclusive security pacts with countries across the region – including a policing agreement with Tuvalu last year, and a treaty with Nauru unveiled earlier this week.

Some have lauded the pact with PNG - which declared independence from Australia in 1975 - as another major strategic win for Australia.

"Over the past couple of years, with the heightened geopolitical interest and engagement in the Pacific, something a lot of other middle powers and major powers have struggled to do is to get PNG on a deal of exclusivity for security partnerships," said Oliver Nobetau, a PNG government lawyer turned policy analyst at the Lowy Institute think tank.

Both prime ministers have sought to downplay the security aspect of the deals, framing them instead as a boon to what Mr Nobetau says has been a "thinning" relationship between the two countries.

Marape made a point to say the agreement "doesn't stop us from relating with any nation, especially our Asian neighbours".

"We relate with China, for instance, a great trading partner, a great bilateral partner," he said. "But in security, closer to home… our shared territory needs to be protected, defended, policed… together."

Government sources say the deals do not give Australia veto power over PNG security agreements. But their framing does have the effect of eliminating almost every other potential partner - and Mr Nobetau said the announcement could be seen by some in PNG as "an exertion of Australian power over PNG sovereignty".

Both he and Dr Murray also note, however, that the dual deals speak to an emerging "transactional" dynamic in Pacific relations.

"People that talk about goodwill and who say sport and politics don't mix, that's the 20th century view," Dr Murray said. "For us, there's no way we're going to give away one of our prize cultural assets for nothing. That doesn't happen in diplomacy."

Dr Murray and Mr Nobetau also both agree that the deals mark a significant moment in bilateral relations between the two countries - and are a likely indicator of how Australia is going to continue to pursue its agenda across the region.

"China puts in a lot of money into sport infrastructure… which is sort of what China is good at… [but] China is not going to be offering any alternatives in this space," Mr Nobetau said.

"It's something that other countries can't do," Dr Murray added. "We need to use it, especially in a very, very contested region such as the Pacific."