North Korea's Vice Foreign Minister has issued an ominous warning after US President Donald Trump called the country a "problem [that] will be taken care of".
"We've got a powerful nuclear deterrent already in our hands and we certainly will not keep our arms crossed in the face of a US pre-emptive strike," Han Song-ryol said.
"If the US comes with reckless military manoeuvres, then we will confront it with the DPRK's pre-emptive strike."
On Thursday, soon after the US dropped its biggest non-nuclear bomb in combat on an Islamic State target in Afghanistan, Mr Trump denounced North Korea as a problem.
"North Korea is a problem. The problem will be taken care of," he said.
Mr Han said Mr Trump's "aggressive words" were being seen as a threat.
"Whatever comes from the US politicians, if their words are designed to overthrow the DPRK system and government, we will categorically reject them," he said.
"As I said, Trump is always using aggressive words - it is the US that is threatening us."
On Twitter, Mr Trump said he had "great confidence" China would "properly deal with North Korea".
"If they are unable to do so, the U.S., with its allies, will! U.S.A.," he wrote.
He followed with a second tweet reassuring his country "things will work out fine" with Russia, promising: "At the right time everyone will come to their senses & there will be lasting peace!"
But the Kremlin is also wary of the growing tensions, with Vladimir Putin's spokesperson Dmitry Peskov saying countries need to "show restraint".
"Moscow is watching the escalation of tension around North Korea with great concern. We call on all the countries to show restraint and warn them against any actions which could start some kind of provocation," he said on Friday.
"And of course, Russia keeps its stable position and stays on the side of solving the situation by political and diplomatic means in all the crises, including the North Korean crisis."
The rising tension has also put China on guard, with foreign minister Wang Yi warning conflict between the two could break out at any moment.
"We call on all parties to refrain from provoking and threatening each other, whether in words or actions, and not let the situation get to an irreversible and unmanageable stage," he said.
China is North Korea's only backer but fears the regime collapsing and causing problems along its border.
Mr Han said North Korea will continue amping up its military and nuclear capabilities while the US remains a "threat".
"We are taking into account the most aggressive and dangerous option that the US might come up with and we have also got our options, our countermeasures ready in our hands, which means we'll go to war if they choose," he said.