An aircraft carrier the United States said 11 days ago was sailing to waters off the Korean Peninsula in response to Pyongyang's recent missile launches was in fact heading in the opposite direction, the US armed forces admitted yesterday.

The April 8 announcement that the USS Carl Vinson was cancelling a planned trip to Australia and was instead heading north from Singapore prompted speculation about a US pre-emptive strike on North Korea.

US President Trump even told Fox Business Network, "We are sending an armada, very powerful."

However, yesterday the US Pacific Command said that while it had cancelled a planned port visit to Perth, the USS Carl Vinson and accompanying warships had in fact headed to north-west Australia to take part in planned exercises.

The strike group was now heading north to the Western Pacific "as a prudent measure," a spokesperson said.

The confusion came to light after the US Navy posted online a picture of the USS Carl Vinson passing through the Sunda Strait, the waters between the Indonesian islands of Java and Sumatra, last Saturday.

The outlet Defense News first reported on the photograph on Monday, noting that the straits is around 5,400 kilometres from the Korean Peninsula.

A Pentagon spokesperson refused to comment on when the strike group, which also included two guided-missile destroyers and a guided-missile cruiser, would arrive off the Korean Peninsula.

However Defence Department officials cited by the New York Times said the carrier was expected next week.

- dpa