When US president Donald Trump boasted early last week that he had sent an "armada" as a warning to North Korea, the aircraft carrier strike group he spoke of was still far from the Korean peninsula, and headed in the opposite direction.

It was even farther away over the weekend, moving through the Sunda Strait and then into the Indian Ocean, as North Korea displayed what appeared to be new missiles at a parade and staged a failed missile test.

The US military's Pacific Command explained on Tuesday that the strike group first had to complete a shorter-than-initially planned period of training with Australia. But it was now "proceeding to the Western Pacific as ordered," it said.