The US Navy "armada" said to be heading towards the Korean peninsula to deter nuclear testing was actually carrying out exercises in the Indian Ocean thousands of kilometres away.
The US government said last week the USS Carl Vinson aircraft carrier was in a group being dispatched to the Sea of Japan to send a "powerful signal" to North Korea.
The move was apparently made over fears North Korea would carry out a sixth nuclear test. It also followed the country's administration criticising a US attack on a Syrian air base, saying it was an "intolerable act of aggression against a sovereign state".
"We are sending an armada. Very powerful," US President Donald Trump told the Fox Business Network.
"He is doing the wrong thing," he said of North Korean leader Kim Jong-un. "He's making a big mistake."
North Korea said it was prepared to respond to any US aggression.
The Vinson's strike group had been scheduled to make port visits to Australia, but on 8 April the US Pacific Fleet announced it would "sail north and report on station in the Western Pacific Ocean after departing Singapore".
But, instead of heading straight towards the Korean peninsula, the US strike group instead conducted planned exercises with HMAS Ballarat in the Indian Ocean.
Senior Australian defence sources said the US carrier group was now gradually making its way closer to North Korea.
According to images released by the US Navy, it passed north through the Sunda Strait - the passage between the Indonesian islands of Sumatra and Java about 5600km from Korea - on Saturday.