WASHINGTON (AFP) - President Donald Trump said military action against North Korea was not the "first choice" of his administration on Wednesday (Sept 6), edging away from his most bellicose threats against the Pyongyang regime.

After a phone call with Chinese counterpart Xi Jinping about how to deal with Kim Jong-Un's threatening nuclear and ballistic missile programs, Trump did not rule out military strikes if necessary.

But, he indicated, other avenues for pressure would come before military action.

"Certainly that's not our first choice, but we will see what happens," Trump said as he boarded Marine One at the White House.

Trump has previously warned of "fire and fury" if North Korea continued tests and warned its few international partners that trade with the United States could come to an end.

So far, those threats have gone unheeded in Pyongyang which recently detonated an apparent thermonuclear bomb.

That and a litany of other tests appear aimed at marrying missile and nuclear technology in a way that could put the United States within striking distance.

Trump has accused China in particular of not doing enough to tighten economic pressure on its smaller neighbor. But on Wednesday Trump sounded more conciliatory.

"I believe that President Xi agrees with me 100 per cent. He doesn't want to see what's happening there, either. We had a very, very frank and very strong phone call."

After years of incrementally tougher sanctions against North Korea, the United Nations is currently weighing additional steps.

Those could include an squeezing oil supplies or restricting North Korea's ability to collect remittances from workers abroad.