The formal alliance, just the third in Australian history and the first in more than 70 years, puts PNG on the same level of partnership as the United States and New Zealand.

It includes mutual defence obligations, requiring either nation to come to the aid of the other if it is ever attacked, and sets up a pathway for PNG citizens to enlist with the Australian Defence Force.

“I say on behalf of the government and the people of Australia, we consider it a great honour that our nearest neighbour is our newest ally,” Albanese said. 

“This treaty contains a mutual defence obligation similar to Australia’s ANZUS Treaty, where we declare in the event of an armed attack on either of our countries, we would both act to meet the common danger.”

The treaty, which was proposed by Marape, was slated to be signed last month, only for PNG to be unable to put together a cabinet quorum to approve it amid celebrations for the 50th anniversary of the young nation’s independence.

While the agreement comes as China seeks to extend its influence in the Pacific, both leaders insisted the treaty was solely about the relationship between Australia and PNG.

“This treaty was not conceived out of geopolitics or any other reason, but out of geography, history and the enduring reality of our shared neighbourhood,” Marape said.

“It is about one bigger fence that secures two houses that has its own yard space. It is in this construct that we’re going about in signing this treaty.”

But at the same time, it secures Australia’s defence position in its closest neighbour, and Albanese said that, under the treaty, “both of the nations have also agreed not to undertake any activities or enter into any agreements that would compromise the implementation”.

“Today, we have a cracker of a result,” the prime minister added.

The full text of the treaty will be publicly released by the government and must still be ratified by both nations’ parliaments.