U.S. and allies must work more closely on N.Korea - Japan expert

The United States, South Korea and Japan must coordinate more closely on North Korea, with whom they are engaged in a "pre-negotiation bargaining process", a former Japanese defence official told Reuters.

North Korea's Kim Jong Un has shown no sign of willingness to give in to U.S. demands and negotiate away a nuclear and missile programme, in defiance of United Nations Security Council sanctions.

But despite the tensions between Washington and Pyongyang, the two Koreas held their first talks in two years on Tuesday and agreed to meet again.

The United States and its regional allies have taken a "coercive military option" by using B-1B bombers, stealth fighters, and aircraft carriers, Narushige Michishita, professor at Japan's National Graduate Institute for Policy Studies said in an interview at the Geneva Centre for Security Policy (GCSP).

"We are kind of testing North Korea's ability to respond ... We are collecting information as to the intentions and capabilities of North Korea armed forces," he told Reuters.

"By conducting different military actions, one of the objectives that the U.S. might have is to drive a wedge between political leaders and military leaders inside North Korea," he added.

North Korea has made no secret of its plans to develop a missile capable of hitting the U.S. mainland and has fired two missiles over Japan, putting Tokyo in range.

However, Michishita said he did not expect U.S. President Donald Trump to undertake a preventive strike.

"In order to destroy an important part of North Korea's nuclear and missile programmes, you have to really undertake a major war against North Korea almost. Conventional, but a major war," Michishita said.

Any attack would need to destroy North Korea's nuclear and missile programmes as well as conventional weapons such as long-range artillery and rocket launchers aimed at Seoul, he said.