In what will mark his fourth visit to Australia's closest northern neighbour, Pat Conroy will attend a meeting of 18 Pacific island leaders alongside US Secretary of State Antony Blinken.
US President Joe Biden was scheduled to attend to sign the pact on his way to Australia for the Quad meeting but both trips have been cancelled so he can continue negotiations with Congress over the debt ceiling to avoid a catastrophic default.
Mr Biden will instead host a Pacific leaders summit in Washington in September.
The US-pact stirred concern among PNG opposition politicians who feared it could jeopardise the country's "friends to all, enemies to none" foreign policy by giving America a military foothold.
PNG Prime Minister James Marape worked to quell concerns saying a framework pact would be signed on Monday and "how we deal with boots on the ground, how we deal with contractors on the ground" would be worked on.
Australia is also negotiating its own defence agreement with Port Moresby. Talks were scheduled to be wrapped up in April with the pact signed in June.
Progress has been made in recent weeks but a final agreement is yet to be reached.
Mr Conroy said he welcomed increased US involvement in the region and called it "a Pacific nation".
He said he hadn't seen the full details of the American defence pact but noted it was an extension of an agreement that had been in place since 1989.
"What they do with the United States is a matter for them, but we've got a record of working with Papua New Guinea," he told ABC News from Port Moresby.
"There are (Australian Defence Force) personnel embedded over here in Papua New Guinea and we're negotiating a bilateral security treaty right now."
He said negotiations were going well and he's hopeful a deal will be struck soon.
"It's a broad treaty and it's being negotiated in good spirit, and I'm confident that we will reach closure quite soon," he said.
Mr Conroy said his priority was to listen to the views of local leaders and that his visit reflected Australia's deep commitment to the region.
The minister will also meet with local aged care workers who are set to travel to Australia under the Pacific labour scheme, and announce $6.6 million to improve monitoring and managing coral reefs for island communities.
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