The US on Thursday vowed to step up economic sanctions to force North Korea to resume talks over its nuclear programme, underlining that its past efforts had failed to halt Pyongyang's "unlawful" weapons programmes.
Briefing senators at the White House, top Trump administration officials said President Donald Trump wanted to use diplomatic measures and tighten sanctions to pressure Kim Jong-Un's regime.
The senators earlier were ferried in a bus from the US capitol to the White House for an unusual detailed briefing from the Trump administration officials on the current situation in North Korea.
President Donald Trump himself dropped by at the briefing, which was addressed by his top national security aides -- Secretary of State Rex Tillerson, Defence Secretary James Mattis, Director of National Intelligence Dan Coats and Chairman of the Joint Chiefs of Staff Gen Joe Dunford.
"Past efforts have failed to halt North Korea's unlawful weapons programmes and nuclear and ballistic missile tests.
With each provocation, North Korea jeopardises stability in Northeast Asia and poses a growing threat to our allies and the US homeland," the three top officials Tillerson, Mattis and Coats said in a joint statement after the meeting.
North Korea's pursuit of nuclear weapons is an urgent national security threat and the top foreign policy priority, they said, adding that upon assuming office, Trump ordered a thorough review of US policy pertaining to the North Korea.
"The president's approach aims to pressure North Korea into dismantling its nuclear, ballistic missile, and proliferation programmes by tightening economic sanctions and pursuing diplomatic measures with our allies and regional partners," the statement said.
It said the Trump administration is engaging responsible members of the international community to increase pressure on North Korea in order to convince the regime to de-escalate and return to the path of dialogue.
"We will maintain our close coordination and cooperation with our allies, especially the Republic of Korea and Japan, as we work together to preserve stability and prosperity in the region.
"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 three top Trump administration officials said in a statement.
Top American Senators, who had a rare bus ride from the Capitol to the White House, acknowledged that this was an unusual briefing.
At the same time, they differed on partisan lines on the context and importance of the briefing.
"In my congressional career, there s never been a similar type of meeting held at the White House. (But) I don't want to read too much into this," Democratic Senator Ben Cardin, Ranking Member of the Senate Foreign Relations Committee told reporters after the briefing.
"It was encouraging to see virtually every senator there, both Democrats and Republicans, and it was a long and detailed briefing," Republican Senator Ted Cruz told reporters after the meeting.
Cruz said he was "cautiously optimistic that we are seeing early signs that China is helping and cooperating and reining in North Korea....Time will tell".
"I don't want to get into the details of the briefing itself, but I think it's clear that they are going to take more steps, and steps to pressure China as well as others in the region, to get the results we need, which is peaceful denuclearization," said Senator Cory Gardner, who is a member of the Senate Foreign Relations Committee.
"North Korea's reckless belligerence threatens our allies in the region and could possibly threaten the homeland in the future," said Senator David Perdue.
"Today's briefing signals President Trump's willingness to engage and inform both Republicans and Democrats in Congress of the increasing risk posed by North Korea.
"A strong US partnership with our allies in the region is essential to reining in this rogue nation and sending the message that this threatening behaviour will not be tolerated," Perdue said.
A senior administration official told reporters that the White House is looking at broad range of options.
"We're looking at a broad range of options, obviously, across all elements of national power and multinational power in connection with North Korea. And so what the president has done is he's made a decision for us to pursue a certain course, and that course obviously has a number of options associated with it, depending on how the situation develops in the future," the official said.
"So I think that what you've seen is really an integrated effort to prioritise diplomatic and informational aspects of national power, but also what you'll see soon is using the economic dimension of national power, as well as the military preparations that are underway," said the official, who spoke on condition of anonymity.
According to the Senior Administration official, North Korea poses a serious threat to the US.
An American response to North Korean threat involves both economic and military options, he said.
"Some of the economic actions take time to develop. What we're endeavoring to do is to work with partners in the region and others to isolate the North Korean ballistic missile programme and the nuclear programme from any sort of external support," the official said.
"If you just look at the images, right, of the big parade there recently and look at the complexity of that equipment, those components, even the tires, right, are not made in North Korea.
"So it's clear that all of us have a lot more to do to isolate the regime from its access to the kind of materials and technologies and components it needs to advance those two very dangerous programs," the official added.
Some of the Democratic Senators said they learnt little from the White House briefing.
"It was a sobering briefing, and an important opportunity for the entire Senate to hear the emerging plans of the Trump administration to confront what is a very real threat to our security," said Senator Chris Coons.
After the briefing, Republican Senator John Boozman said Trump and his national security team have a clear grasp on the urgent need to address the escalating situation with North Korea.
"As Kim Jung Un continues to threaten the US and our allies, it is important that my colleagues and I have all the intelligence necessary to determine the best way forward. The bottom line is that Kim has to end his belligerent actions.
"If not, Congress and the administration need to leave every option on the table to counter these aggressions," Boozman said.