North Korea says the US will be wholly accountable for the catastrophic consequences.
North Korea denounced Washington's deployment of a naval strike group to the Korean peninsula on Tuesday, saying it was ready for "war."
The US Navy's USS Carl Vinson strike group cancelled a planned trip to Australia this weekend to head to the region, in a show of force as Washington signalled it may act to shut down Pyongyang's nuclear capabilities.
"This goes to prove that the US reckless moves for invading the DPRK have reached a serious phase," a spokesperson for the North's foreign ministry said according to state news agency KCNA.
"The DPRK is ready to react to any mode of war desired by the US."
TRT World spoke to Joseph Kim in Seoul for more on the story.
President Donald Trump, fresh from ordering a missile strike on Syria that was widely interpreted as a warning to North Korea, has asked his advisers for a range of options to rein in Pyongyang, a top US official said on Sunday.
Trump has previously threatened unilateral action against Pyongyang if China — the North's sole major ally — fails to help curb its neighbour's nuclear weapons ambitions.
But Pyongyang's response suggested the reclusive state is determined to continue on its current path, despite repeated rounds of United Nations sanctions.
"We will take the toughest counteraction against the provocateurs in order to defend ourselves by powerful force of arms," the foreign ministry spokesman said.
"We will hold the US wholly accountable for the catastrophic consequences to be entailed by its outrageous actions."
Seoul and Washington are also currently conducting joint military drills, an annual exercise which is seen by the North as a preparation for invasion.
South Korea's top nuclear envoy said on Monday after talks with his Chinese counterpart that the two nations had agreed to "strong" new measures to punish Pyongyang if it carried out another nuclear test.
The talks came shortly after Trump hosted Chinese leader Xi Jinping for a summit at which he pressed Beijing to do more to curb the North's nuclear ambitions.
"(We) are prepared to chart our own course if this is something China is just unable to coordinate with us," US Secretary of State Rex Tillerson said after the summit.