Pyongyang: North Korean state media warned on Tuesday of a nuclear attack on the United States at any sign of American aggression as a US Navy strike group steamed toward the western Pacific.

US President Donald Trump, who has urged China to do more to rein in its impoverished ally and neighbour, said in a Tweet that North Korea was "looking for trouble" and the United States would "solve the problem" with or without Beijing's help.

Tension has escalated sharply on the Korean peninsula amid concerns that reclusive North Korea may soon conduct a sixth nuclear test and after Washington said at the weekend it was diverting the aircraft carrier strike group Carl Vinson toward the Korean peninsula in a show of force.

US officials have stressed that stronger sanctions are the most likely US course to press North Korea to abandon its nuclear program, but Washington has said all options - including military ones - are on the table. It said a US strike last week against Syria should serve as a warning to Pyongyang.