The Trump administration is ratcheting up its campaign against North Korea, summoning all 100 US senators to the White House. There, top defence officials declared that defending the US from a possible nuclear attack has become a top priority. However, by the meeting's end, a number of senators seemed bewildered, saying they still didn't know what the White House's policy on North Korea was, and that the briefing lacked straight answers. The unusual classified gathering came after the top US military officer in the Pacific said the Pentagon needed to consider deploying new anti-ballistic missile systems and a defensive radar to Hawaii to protect that island state against a growing threat from North Korea.
"Kim Jong Un is clearly in a position to threaten Hawaii today, in my opinion," Admiral Harry Harris, the chief of US Pacific Command, told the House Armed Services Committee. "I have suggested that we consider putting interceptors in Hawaii that ... defend (it) directly, and that we look at a defensive Hawaii radar."
President Donald Trump has dispatched additional military resources to the region following North Korea's engagement in a series of weapons tests in recent months, but aides say he hopes to use additional economic sanctions and diplomacy before resorting to military options.
Trump's top advisers described North Korea's pursuit of nuclear weapons as an urgent national security threat and, for the first time, his top foreign policy priority.
Trump offered to play host to the meeting - open to all 100 senators, who arrived on a large white bus - as a courtesy after Senate Majority Leader Mitch McConnell, Republican-Kentucky, asked for the briefing in the wake of increased tension on the Korean Peninsula, officials said. The meeting came as the US military had redirected the USS Carl Vinson aircraft carrier strike group toward the region in response to a failed North Korean missile test last week.
But senators departing the briefing expressed frustration that the administration shared few details of its current policy on North Korea and its plans to deal with the country as it continues developing its nuclear weapons programme.
"They're trying to do the right thing," said one Republican senator, but members of both parties left frustrated that they were given "very few details about what has changed". The briefing lacked "even straight answers on what the policy is regarding North Korea and its testing of ICBMs", said the senator, who requested anonymity to speak frankly about the meeting.
"Several senators asked specifically, 'what is the policy?' and the briefers gave us very, very few details," the senator said.
The goal is to "convince the regime to de-escalate and return to a path of dialogue" toward peaceful denuclearization of the Korean Peninsula, they said. "We remain open to negotiations to towards that goal. However we remain prepared to defend ourselves and our allies."
The Republican senator said "the basic gist of it at the beginning was that we're going to get more aggressive, we've waited and they've continued to be bad actors. We've reached a point where things are getting pretty dire and getting to the point where we've got to get more aggressive."
Trump and Vice President Mike Pence briefly addressed the senators at the beginning of the meeting.
When they left, senators heard from Secretary of State Rex Tillerson, Defense Secretary Jim Mattis, Daniel Coats, the national intelligence director, and General Joseph Dunford Jr, chairman of the Joint Chiefs of Staff. Just a handful of staffers were in the room with the four briefers.
In a joint statement, Tillerson, Mattis and Coates called North Korea's pursuit of nuclear weapons "an urgent national security threat and top foreign policy priority". They said Trump's approach aimed to tighten economic sanctions and pursue "diplomatic measures" with allies and partners.
The United States seeks stability and the peaceful denuclearization of the Korean peninsula. We remain open to negotiations towards that goal.
"However, we remain prepared to defend ourselves and our allies."
The Republican senator said: "The basic gist of it at the beginning was that we're going to get more aggressive, we've waited and they've continued to be bad actors. We've reached a point where things are getting pretty dire and getting to the point where we've got to get more aggressive.
"From then on, what we all wanted to know is, 'what does that mean?'," the senator added.
"What is it that we should be looking for as the trigger that something is about to happen and that we'd end up taking some kind of kinetic action? That's where things got a little elliptical."
The briefing lasted more than an hour, and several senate Democrats and Republicans praised the administration for saying North Korea was its top priority.
"The military is obviously planning for a number of contingencies and a number of options, as well they should, and running a full range from a more minimal military action to a far more significant military action," said Senator Ted Cruz, Republican-Texas.
"If there is a clear and imminent threat to the United States, our military needs to be prepared to act. I believe our military is prepared to act to keep our nation safe."
Some senators said they hoped Trump would continue to work with Chinese President Xi Jinping on North Korea. The two had spoken as recently as Monday.
China has significant leverage with North Korea, with 80 per cent of North Korea's economy depending on ties to the nation. But defence officials say Pyongyang is unlikely to abandon its nuclear weapons program no matter how much pressure its main ally applies.
Senator Chris Coons, Democrat-Delaware, called the meeting "sobering" and said it was clear that North Korea "intends to develop nuclear weapons and the capability to deliver them".
"It is my hope that sustained and effective diplomatic engagement by the Trump administration with China will lead China to take actions they haven't taken previously," he said.
The briefing for the senators on White House grounds was a departure from normal procedure, when such briefings are held in secure, underground auditoriums or conference rooms at the US Capitol. Those rooms are built to withstand digital eavesdropping.
"There was a definite degree of resolve that we've got a bad situation on our hands and they're ratcheting up the importance of this," the Republican senator said. "One of the things that I surmised from it was that as much as anything else, perhaps they wanted to prepare everybody for the fact that this could escalate quickly. That's my own read on it."
North Korea conducted live-fire artillery drills this week near the city of Wonsan on the east coast, according to the country's official media.
"In the time I've been doing this, I would say that the conditions for a miscalculation by someone which could cause a military response has never been higher, and that's primarily due to the character of the person who's the head of North Korea right now," said Idaho Republican Senator Jim Risch, a member of the Senate's Intelligence and Foreign Relations committees.
Aircraft from the USS Carl Vinson strike group, which has positioned itself in the Philippine Sea, can now reach North Korea in a two-hour flight. Harris of Pacific Command dismissed North Korea's threats to sink the aircraft carrier and its strike group, saying, "If it flies, it will die."
A nuclear-powered submarine, the USS Michigan, was in the area for what has been described as a routine visit while a pair of American destroyers were conducting exercises from South Korea and Japan.
A US advanced missile-defence system that is being installed in South Korea will be operational in a few days, Harris said.
The US and South Korea agreed to deploy the US$800 million (NZ$1.1 billion) system last July in a deal brokered under the now-impeached South Korean president, Park Geun Hye.
The Terminal High-Altitude Area Defence battery, which is manufactured by Lockheed Martin, can target short, medium and intermediate-range ballistic missiles in flight. China and Russia have opposed the defense system, saying it undermines their own security interests.