North Korea has conducted several missile and nuclear tests in defiance of United Nations sanctions and has said it has developed a missile that can strike the US mainland. Its latest missile test on Sunday failed a few seconds after launch.
US Vice President Mike Pence warned North Korea on Monday that recent US strikes in Syria, one of Pyongyang's few close allies, and Afghanistan showed that the resolve of President Donald Trump should not be tested.
"We'll be conducting more missile tests on a weekly, monthly and yearly basis," Vice Foreign Minister Mr Han Song-Ryol said in an interview with the BBC released late on Monday.
"If the US is reckless enough to use military means it would mean from that very day, an all out war."
North Korean state media last week warned of a nuclear attack on the United States at any sign of American aggression, but the White House said there was no evidence it possessed that capability.
"If the USA is planning a military attack against us we will react with a nuclear pre-emptive strike by our own style and method," Han said.
He also said North Korea believed its nuclear weapons protect it from the threat of military action by the United States.
(Reporting by Kylie MacLellan, Editing by Jeremy Gaunt)