In an interview with the BBC on Monday, Vice Foreign Minister Han Song-Ryol said, "We'll be conducting more missile tests on a weekly, monthly and yearly basis".
US President Donald Trump has said that will not happen, and stepped up pressure on the isolated North.
"This is a frontier of freedom", Vice President Mike Pence said on Monday as he visited the Demilitarized Zone dividing North and South Korea. On Thursday, the US military dropped "the mother of all bombs", the largest non-nuclear device it has ever unleashed in combat, on caves and tunnels used by Islamic State in Afghanistan. Its latest missile test on Sunday failed a few seconds after launch.
"The Trump administration, which made a surprise cruise guided missile strike at Syria on April 6, has entered the path of open threat and blackmail against (North Korea)", a spokesman for the Korean People's Army said according to state news agency KCNA.
Vice President Mike Pence warned in Seoul today that North Korea "would do well not to test" the "resolve" of President Trump, "or the strength of the Armed Forces of the United States in this region". On Thursday, the USA military said it had dropped "the mother of all bombs", the largest non-nuclear device it has ever unleashed in combat, on a network of caves and tunnels used by Islamic State in Afghanistan.
The unannounced visit Monday at the start of his 10-day trip to Asia was a USA show of force that allowed the vice president to gaze at North Korean soldiers from afar and stare directly across a border marked by razor wire.
He warned that as long as the United States and its allies "scheme to bring down the socialist system in the DPRK", the government will keep increasing "its military muscle" to protect the country.
Pence told reporters that the North Korean people and military "should not mistake the resolve of the United States of America to stand with our allies", calling the alliance "iron-clad". While visiting United States ally South Korea over the weekend, Pence warned that Washington's attitude toward North Korea has changed sharply.
Earlier, Pence told reporters at the DMZ that "the era of strategic patience is over".
"Over the past 18 months, North Korea has conducted two unlawful nuclear tests and an unprecedented number of ballistic missile tests, even conducting a failed missile launch as I traveled here for this visit".
A customer service representative for Air China, the only foreign carrier operating a regular commercial flight to North Korea, said Monday it had cancelled the flights due to low demand.
In recent months it has demonstrated signs that it wants to help the global community force North Korea to back down - in February it banned all coal imports from the country and last week deployed 150,000 troops to the border.
He added that the U.S. could face "all out war" if Donald Trump and his government were "reckless enough to use military means".
Russia's Foreign Minister Sergei Lavrov said Moscow would not tolerate "missile adventures by Pyongyang" but a unilateral use of power by the United States would be "a very risky course".
He said the United States insists "on the gangster-like logic that its invasion of a sovereign state is "decisive, just and proportionate" and contributes to "defending" the worldwide order in its bid to apply it to the Korean peninsula as well".
How advanced is North Korea's nuclear programme?