Open to negotiations with North Korea: Trump

US President Donald Trump has said he is open to the possibility of negotiations with North Korea over its nuclear weapons programme.

"We're going to see what happens with North Korea. That's all I can say. We're going to see what happens. We're totally prepared for numerous things," Donald Trump told reporters on Friday at the White House, Efe news reported.

"If something can happen where we negotiate, I'm always open to that. But if it's going to be something other than negotiation, believe me, we are ready, more so than we have ever been," he added.

Two weeks ago, Trump was dismissive of remarks by his secretary of state, Rex Tillerson, indicating the US had established direct lines of communication with North Korea and was interested in dialogue.

"I told Rex Tillerson, our wonderful Secretary of State, that he is wasting his time trying to negotiate with Little Rocket Man," Trump tweeted on October 1, using his nickname for North Korean supreme leader Kim Jong-un.

"Save your energy Rex, we'll do what has to be done!" Trump added.

A day after that tweet, White House Press Secretary Sarah Sanders said the "only conversations that have taken place" with Pyongyang "would be on bringing back Americans who have been detained."

"Beyond that, there will be no conversations with North Korea at this time," she added.

Trump ominously warned Pyongyang in his debut speech before the United Nations General Assembly on September 19 that the US would obliterate the secretive Asian country if necessary.

"The US has great strength and patience, but if it is forced to defend itself or its allies, we will have no choice but to totally destroy North Korea," Trump said in his UN speech.

Shortly afterward, Kim accused Trump of being mentally deranged and said he would "pay dearly" for making threats against North Korea.

The Asian nation's foreign minister, Ri Yong-ho, told reporters in New York on September 22 that North Korea may retaliate for Trump's threats by testing a hydrogen bomb in the Pacific Ocean.