US President Donald Trump has declared he is "locked and loaded" to respond to Tehran's alleged role in the bombing of Saudi oilfields.

Australia has already joined a US-led maritime mission to protect oil ships in the Strait of Hormuz.

But as he prepares to fly to Washington, Scott Morrison has dismissed questions about offering the US support for direct military action.

"I think it is very premature and none is being asked for," Mr Morrison told the Nine Network on Wednesday.

"The US statement was a statement of capability, not necessarily intention.

"So I think that we have to act cautiously and sensitively in this area. I am sure it will be one of many issues that get discussed about the geo-strategic situation at the moment."

Australian Associated Press