Donald Trump's administration has embarked on a more forceful United States stance toward North Korea's recent missile tests and threats, including a warning from the president that the North Korean leader has "gotta behave".
Trump made the off-the-cuff comment to a CNN reporter after kicking off the 139th annual Easter egg roll with First Lady Melania Trump.
The North's Foreign Ministry said the missile launches were part of a normal process of building up the country's defences and economy.
The tensions between the US and North Korea are spiking as North Korea has been posturing toward an attack, celebrating with military parades and conducting failed missile tests.
Pence also said on Tuesday that all options were on the table in dealing with North Korea, but that President Donald Trump is determined to work with Japan, China and South Korea to find a peaceful solution. He made clear that Beijing would cooperate in exerting pressure but not endorse solo actions like the USA attack on Syria.
Donald Trump's number two issued the explosive warning from the windswept deck of a massive U.S. aircraft carrier during a visit to Japan.
"In the case of our super-mighty preemptive strike being launched, it will completely and immediately wipe out not only USA imperialists' invasion forces in South Korea and its surrounding areas but the US mainland and reduce them to ashes", it said.
Speaking aboard the nuclear-powered USS Ronald Reagan aircraft carrier docked at the U.S. Navy's Yokosuka base, Pence said a diligent and collaborative approach to deescalating tensions on the Korean Peninsula was the way forward.
Mr Pence's comments come after a senior North Korean official warned that the regime had no intention of dialling down its missile programme, pledging weekly tests and threatening "all-out war" if the United States took any action against it.
He also said the United States will honor its alliance with Pacific Rim nations to protect freedom of navigation in the disputed South China Sea - most of which Beijing lays claim to, despite conflicting claims from other Asian nations.
The recent surge in tensions on the Korean Peninsula finds Beijing on the outs with both North and South Korea, while many critics have yet to be convinced by its insistence that its influence with Pyongyang has been exaggerated.
"If the United States of America is planning a military attack against us we will react with a nuclear pre-emptive strike by our own style and method", Han said. "We are with you 100 percent", he said.
Mr Mattis credited China with trying to help get the North Korea situation "under control" with the goal of denuclearising the peninsula. But the vice-president expressed impatience with the unwillingness of North Korea to rid itself of nuclear weapons and ballistic missiles.