After a short delay and much speculation, Australia and Papua New Guinea have signed a formal alliance , cementing Canberra's position as the security partner of choice for its closest neighbour, even as China seeks to increase its influence in the region.

Prime Minister Anthony Albanese and his PNG counterpart James Marape this afternoon put pen to paper on the mutual defence agreement, also known as the Pukpuk Treaty.

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

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