Jim Mattis criticises North Korea for its 'provocative acts'

US Senate Foreign Relations Committee discussed North Korea for the first time under Trump this week

In his first public remarks abroad as US Defence Secretary Jim Mattis on Thursday criticised North Korea for provocative acts and said he would consult with South Korean and Japanese officials about whether the current strategy for getting the North to curtail or eliminate its nuclear and missile programmes is adequate.

Mattis spoke to reporters aboard his military plane en route to Osan air base from Washington. In the brief interview, he said he would be discussing the plan to install a new US missile defence system, called the Terminal High Altitude Area Defense (Thaad), in South Korea as a means of deterring the North's ballistic missile threats against South Korean and Japan.

North Korea also has said it is nearly ready to test-launch a ballistic missile of intercontinental range, meaning it could theoretically threat the United States.

"Were it not for the provocative behaviour of North Korea, we would have no need for Thaad out here," Mattis said.

Alluding to China's objections to having Thaad deployed in South Korea, Mattis said, "Thaad should be a worry to no nation other than North Korea."

Mattis held an introductory meeting with Prime Minister Hwang Kyo-ahn, who said he looked forward to working with the Trump administration.

Mattis said he was delivering a message from Trump.

"I talked to President Trump and he wanted to make a very clear statement about the priority that we place on this alliance between our two nations, the secretary said.

"Our new administration inherits a very strong, trusted relationship between our two countries and it's our commitment to make it even stronger especially in the face of the provocations that you face from North Korea."

After a series of meetings in Seoul on Thursday and Friday, Mattis was scheduled to fly to Tokyo for further consultations.

In Washington this week, the Senate Foreign Relations Committee held its first policy hearing since Trump took office to discuss North Korea. There were more questions than answers.

Last month, Trump fueled speculation of possible US military action to pre-empt North Korea's weapons development. In response to Kim's threat, Trump tweeted, "It won't happen!" But he didn't elaborate how he could be so sure.

"Does that mean we have drawn a red line?" Sen Ben Cardin, D-Md, asked at Tuesday's Senate hearing.

Those questions and more will be posed to Mattis when he meets top officials in Seoul today and Tokyo later in the week, two jittery allies that host nearly 80,000 US troops.

During the campaign, Trump complained that defence treaties disadvantaged the US and that he would not rule out abandoning signatories if they refuse to pay more for their defence.

He also suggested that South Korea and Japan, which are already within the range of North Korean missiles, might acquire their own nuclear weapons rather than rely on US deterrence.