Later Monday, Pence reiterated in a joint statement alongside South Korean Acting President Hwang Kyo-ahn that "all options are on the table" to deal with threat and said any use of nuclear weapons by Pyongyang would be met with "an overwhelming and effective response".
"Whatever change happens in your elections the commitment of the USA to South Korea's safety and security will remain unchanged", Pence said.
The unannounced trip allowed the vice president, whose father fought in the Korean War, to look at North Korean soldiers from afar and gaze directly across a border marked by razor wire.
Former British foreign minister Sir Malcolm Rifkind, suggested Sunday (16 April) that the U.S. was behind North Korea's failed missile launch.
Viewing his adversaries in the distance, U.S. Vice President Mike Pence traveled to the tense zone dividing North and South Korea and warned Pyongyang that after years of testing the U.S. and South Korea with its nuclear ambitions, "the era of strategic patience is over". But Pence expressed impatience with the unwillingness of the regime to move toward ridding itself of nuclear weapons and ballistic missiles.
The Trump administration is focusing its North Korea strategy on tougher economic sanctions, possibly including an oil embargo, a global ban on its airline, intercepting cargo ships and punishing Chinese banks doing business with Pyongyang, Reuters reported last week, citing U.S. officials.
"The era of strategic patience is over, "Pence said".
While Trump has employed tough rhetoric in response to North Korea's recent missile tests, the new U.S. president's options appear limited in dealing with a challenge that has vexed his Oval Office predecessors.
Trump on Sunday acknowledged that the softer line he has taken on China's management of its currency was linked to China's help on the North Korea issue.
Former Clinton spox tweets at Trump over Tax March
Thousands of protesters gathered across the US on Saturday for the Tax March calling Trump release his taxes. Trump had said he was under audit and would release the returns after the IRS finished his audit.
After a two-month policy review, officials settled on a policy dubbed "maximum pressure and engagement", US officials said Friday.
Operations to install the THAAD began in early March, the day after the North launched four ballistic missiles, when the United States flew in the "first elements" of the system to a military base near the South Korean capital Seoul.
The officials weren't authorized to speak publicly on the results of the policy review and requested anonymity.
Meanwhile, Japanese Prime Minister Shinzo Abe has called on North Korea's leader Kim Jong-un to avoid escalating the situation and drop its nuclear program in compliance with United Nations resolutions.
On Friday, North Korea said the unsafe security situation was due to the "Trump administration's reckless military provocation".
Deputy national security adviser K.T. McFarland briefed the president on the failed missile launch. One day earlier, North Korea conducted a massive military parade in Pyongyang to celebrate the April 15 anniversary of founder Kim Il Sung's birthday.
The United States, South Korea and other countries have vowed to apply more pressure on the North, but so far nothing has worked to stop Pyongyang's nuclear programme. The U.S. moves an huge warship to the waters off the peninsula in a display of military might.
The regime followed that - according to US and South Korean officials - with an attempted missile test Sunday from the eastern port of Sinpo.
It has said it has developed and would launch a missile that can strike the mainland United States but officials and experts believe it is some time away from mastering the necessary technology, including miniaturising a nuclear warhead. They have heard North Korean warnings of their destruction for so long that the threats barely even register. Trump tweeted on Sunday. "Our commitment to this historic alliance with the courageous people of South Korea has never been stronger". Recent satellite imagery suggests the country could conduct another underground nuclear test at any time.