The official said that had it been a nuclear test, "other actions would have been taken by the U.S".
A North Korean missile exploded during launch Sunday, U.S. and South Korean officials said, a high-profile failure that comes as a powerful U.S. aircraft supercarrier approaches the Korean Peninsula in a show of force.
The failed launch was at 7.21am AEST.
"The missile blew up nearly immediately".
Pence is travelling to South Korea to hold talks with the country's leadership.
CNN and Reuters cited South Korean military reports regarding the missile attempt, with Reuters saying it was launched from North Korea's east coast.
The statement reportedly added that the president had no further comment at the moment. "Its allies - South Korea and Japan - are also extremely anxious", he said.
The Pentagon and South Korea's Joint Chiefs of Staff said it wasn't immediately clear what type of missile was involved. South Korea has a spotty record of tracking developments in North Korea, as information about the secretive, authoritarian state is often impossible to confirm.
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South Korea's military said they would continue to analyse the test for more details.
In a separate appearance on the Fox Business Network, Trump said that North Korean leader Kim Jong Un was "doing the wrong thing". Recent satellite imagery suggests the country could conduct another underground nuclear test at any time.
Observers paid close attention to the missiles and launchers that were displayed during the colorful military spectacle.
Earlier in the day, South Korean military reported a seemingly failed missile launch by North Korea, with US Pacific Command confirming the information and adding that the missile "blew up nearly immediately".
"Trump is always making provocations with his aggressive words", Han Song Ryol said.
He has repeatedly said if China, North Korea's dominant trading partner, is unwilling to do more to pressure the North, the USA might take the matter into its own hands.
However, John Bolton, America's former ambassador to the United Nations, said piling on pressure wouldn't work and that the U.S. needed China's help to try and bring North and South Korea back together.
"The message, I think, is going to be about vigilance and deterrence", said Victor Cha, the Korea chair at the Center for Strategic and International Studies.
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North Korean state media warned that such "reckless acts of aggression" would be countered with "whatever methods the USA wants to take".
"We've tried persuasion, it's failed, we've tried coercion, it's failed".
On Monday, hundreds of members of the Korean People's Army (KPA) crowded the plaza of the Kumsusan Palace of the Sun in Pyongyang to pay tribute to past leaders and vow loyalty to Kim Jong Un, according to state media Rodong Sinmun.
"The fact is, this regime is never going to voluntarily give up nuclear weapons, they're the ace in the hole", he said.
CNN's Will Ripley in Pyongyang, North Korea, reported there was no immediate confirmation from North Korean state media about the launch.
North Korea said Friday that the US had better not treat it like Saddam Hussein and Moammar Gaddafi, that is, like Iraq and Libya. He then stepped up to a podium and clapped with senior government officials to address the thousands of soldiers and civilians taking part in the parade at Kim Il Sung Square in Pyongyang, the capital.
A series of what appeared to be KN-08 missiles were among the weapons rolled out on trucks.
Kim Jong-un did not speak at the parade but waved from a balcony. Under his watch, North Korea has aggressively pursued a goal of putting a nuclear warhead on an ICBM capable of reaching the USA mainland. He said Pence will try to balance reassurance with a willingness to respond if North Korea acts. The country launched a long-range rocket and conducted the two nuclear tests past year, including its most powerful to date.
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Tottenham cut the Blues' lead at the top of the Premier League table to four points by thrashing Bournemouth 4-0 earlier today. Swansea fell 1-0 to Watford to stay in the drop zone when Etienne Capoue scored the only goal of the game in the 42nd minute.
North Korea conducted two nuclear tests past year alone, advancing its goal to make nuclear weapons small enough to fit on long-range missiles.