US warns of 'significant international response' if North Korea conducts another nuclear test

A State Department official warned Monday that there would be a "significant international response" if North Korea were to mount another nuclear test.

In a conference call with reporters, State Department Acting Assistant Secretary Susan Thornton said the US would not "stand idly by" while North Korea "develops and hones" nuclear weapons.

North Korea, led by authoritarian ruler Kim Jong Un, has conducted five nuclear tests so far. In response to a question about what the US would do in response to a sixth nuclear test, Thornton said that "some kind of major provocation like that would draw pretty significant international response."

"We're definitely not seeking conflict or regime change but we are committed to defending our people and our allies should it be necessary," Thornton said.

In the past, the US has responded to North Korea's nuclear tests by increasing sanctions, which Thornton said the US is also considering.

The Trump administration wants to "maximize economic pressure on the North Korean regime to try to get it to make tangible steps to roll back their illegal programs," Thornton said.

The Kim regime levels a steady stream of threats against the US, and officials say President Donald Trump is watching the country closely. A senior administration official told reporters in February that Trump views North Korea's nuclear program as the "greatest immediate threat" to the US.

On Sunday, North Korea attempted to fire a missile, but it blew up within seconds.

"There is a feeling that this is a very urgent - not just regional, but global - threat at this point," Thornton said. "So I think that when you hear discussion of wanting to evaluate this issue on the priorities list … that reflects the urgency" of the threat.

Despite the warnings issued by the State Department pertaining to another potential North Korean nuclear test, White House press secretary Sean Spicer said Monday that "drawing red lines hasn't really worked in the past." Spicer said Trump won't "telegraph" his plan for a response to other provocations from North Korea.

The US is also hoping that China can increase pressure on North Korea to roll back its weapons program.

"President Trump is very hopeful that the Chinese will use the considerable leverage they have over the economic lifeblood of North Korean economy in the service of this effort," Thornton said. "China has indicated appreciation of the urgency of the threat, of the need to have an international coalition mounted and the need for China to do more in stepping up pressure on the North Korean regime."

Thornton's comments came as Vice President Mike Pence was in Asia visiting the demilitarized zone between the Koreas. Pence said "all options are on the table to achieve the objectives and ensure the stability of the people of this country," warning that "the era of strategic patience" with North Korea "is over."

And Secretary of State Rex Tillerson said last month that the US is considering a preemptive military strike on North Korea if they "elevate the threat of their weapons program to a level that we believe requires action."

Alex Lockie contributed to this report.