Government officials are striking a cautious tone as they prepare to ink a major military treaty between Australia and Papua New Guinea.

The PNG government's cabinet has signed off on the Pukpuk agreement, which will see both countries come to the aid of the other in the event of a military attack.

The island nation's leader James Marape will join Prime Minister Anthony Albanese for Sunday's NRL grand final, and is widely tipped to sign the deal while he's in Australia.

But asked if the agreement would be definitely finalised next week, Defence Minister Richard Marles wouldn't be drawn.

"Let's see how it all unfolds. I just don't want to preempt all of that," he told ABC Radio National.

"This is going to happen imminently," Mr Marles said.

In a statement on Thursday, Mr Marape confir

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