Scott Morrison has hosed down suggestions the US is aiming to put ground-based missiles in Darwin.
The prime minister said the US had not requested a missile deployment in northern Australia after Defence Minister Linda Reynolds poured cold water on the idea.
"It's not been asked of us, not being considered, not been put to us. I think I can rule a line under that," Mr Morrison told reporters in Brisbane on Monday.
At a ministerial meeting on Sunday, Senator Reynolds quizzed-newly appointed US Defence Secretary Mark Esper about reports America wanted to station missiles in Darwin.
"You would expect the US secretary of defence to canvass all of these issues in light of what's happening in the Indo-Pacific," she told ABC Radio National on Monday.
"But I can confirm that he made no request and he wasn't anticipating any request."
US Secretary of State Mike Pompeo says his nation is "constantly" evaluating the way it defends itself, Australia, and the region, including the placement of tools such as missile systems.
"We'll now do the things we need to do to create stability and peace and as we do that we will evaluate whether there are certain systems, certain missile systems that make sense to put in certain countries," he told Sky News during a trip to Sydney for ministerial meetings.
"These will be long, consultative processes as we work our way through them."
Meanwhile, Mr Morrison indicated Australia could join a United States-led international effort to secure shipping in the Persian Gulf, stressing the importance of making the crucial trade route safer.
Canberra is considering joining Washington's efforts to stitch together a global coalition to hit back after Iran captured foreign oil tankers in the Strait of Hormuz.
Mr Morrison said the international effort was about providing freedom of shipping lanes in a sensitive and economically important area.
"It's important that we make the Straits of Hormuz safer than they currently are," he told reporters in Brisbane on Monday.
"The purpose here is to de-escalate tensions, not to escalate them and that has very much been the focus of the conversations we've had with our American partners."
He said it was important to separate the Strait of Hormuz from wider tensions, including the dispute between the US and Iran over nuclear proliferation.
"This is about safe shaping lanes which is is good for global peace," the prime minister said.
The strait is considered the world's most important waterway for oil shipments, with Australia reliant on it for some of its oil supply.
Mr Pompeo said the action in the Persian Gulf aimed to head off a physical conflict and protect the economies of countries including Australia, Japan and South Korea.
He said more than 60 nations had been asked to assist secure commercial passage through the Strait of Hormuz.
"Australia could join in a number of ways. It's a highly capable, sophisticated military. There are many assets it could deploy."