More than 1,000 US marines begin arriving in the Top End and say they are ready for whatever may happen as North Korea escalates its nuclear threat.

The first group of 1,250 marines touched down in Darwin on Tuesday morning for their sixth annual dry season rotation in the Top End.

Their arrival comes as Foreign Minister Julie Bishop defended US President Donald Trump's "they gotta behave" message to North Korean leadership after its failed missile test on Sunday.

"[North Korea] is on a path to achieving nuclear weapons capability and we believe Kim Jong-un has a clear ambition to develop an intercontinental ballistic missile capable of carrying a nuclear payload as far as the US," Ms Bishop said.

"That would mean Australia would be in reach so unless it is prevented from doing so, it will be a serious threat to the peace and stability of our region, and that is unacceptable."

In Darwin, the rotation's commanding officer Lieutenant Colonel Brian Middleton said the force was ready, come what may.

"Any time a marine force is forward deployed, we are always on standby for anything," he said.
He said this year's contingent was "the most robust package" the marines had put together for training in the Top End, featuring an "ace aviation combat element" of 13 aircraft.

Over the next two weeks, the deployment's largest fleet of military aircraft yet will be brought to Australia as part of the agreement, including four high-speed troop transporters, the MV-22 Osprey, five Super Cobra helicopters and four Huey helicopters. The next six months will see the troops train with their Australian counterparts and other nations, including Japan and China.