A permanent Iranian toll on the critical waterway would also be unsustainable, senior ministers say.
After peace negotiations between American and Iranian negotiators collapsed over the weekend, President Donald Trump declared the US Navy will stop "any and all" ships from entering or leaving the key trade route, which until recently carried around one-fifth of the world's oil supplies.
Australia had not been asked to help with the blockade, Prime Minister Anthony Albanese said.
"We've received no requests ... they've made this announcement overnight and they've done that in a unilateral way," he told Nine's Today Show on Monday.
"We haven't been asked, and I don't expect that we will be."
He also called for the strait to reopen and the conflict to end.
The American blockade presented a challenge to international trade at a time when de-escalation was sorely needed, Resources Minister Madeleine King said.
"That poses a very difficult position for global trade," Ms King told the ABC's AM program on Monday.
"Really, the best thing Australia can do is encourage that both parties go back to the negotiating table."
Iran has begun charging a toll for ships wanting to travel through the Strait of Hormuz. Mr Trump has ordered the US Navy to find and intercept any vessel which has paid the toll.
"No one who pays an illegal toll will have safe passage on the high seas," he said on Truth Social.
An ongoing Iranian toll on the strait would be very difficult for Australia and other countries, Ms King said.
"Any suggestion there might be some kind of permanent tolling on an important trade route by a regime that's listed as a terrorist organisation, is just not a sustainable position," she said.
Opposition foreign affairs spokesman Ted O'Brien said any move to join the US blockade needed to meet two key tests: whether it was in Australia's national interest, and whether the military had enough capacity to send troops or equipment.
"It is in our national interest to have the Strait of Hormuz reopened, right? So big tick to that," he said.
"(But) what assets are required? Do we have the capability of sending them?"
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