Speaking in Seoul, Pence linked recent US military strikes in Syria and Afghanistan with the situation in Korea, saying they showed the "strength and resolve of our new president."
"We will defeat any attack and we will meet any use of conventional or nuclear weapons with an overwhelming and effective response," Pence said, adding that when it came to North Korea "all options are on the table."
Amid concerns the US might launch a preemptive strike on North Korea, Pence said Washington would "closely consult" with Seoul "as we make decisions moving forward."
Earlier in the day, Pence visited the Korean demilitarized zone (DMZ), which he described as the "frontier of freedom."
The DMZ is the highly-fortified de facto border
between North and South Korea. It's four kilometers (2.5 miles) wide, stretches 250 kilometers (160 miles) and is dotted with military guard posts, mines and defensive structures.
It was established by the 1953 armistice agreement which ended the Korean War, though both sides technically remain at conflict as no peace treaty has ever been signed.
At the Panmunjom Joint Security Area, which Pence visited Monday, North and South Korean soldiers stand watch feet away from each other, the only place where the two forces come face to face.
Blue huts straddle the border, where tense negotiations have been held between the North, South and the US since armistice.
US options on North Korea
Echoing the remarks of US Secretary of State Rex Tillerson on North Korea last month
, Pence said the "era of strategic patience is over."
The US has leaned on China -- North Korea's main ally -- to apply pressure on Pyongyang to curtail its nuclear ambitions.
At the same it's increased its military footprint in the region by deploying a naval carrier strike group to waters off the Korean Peninsula.
US President Donald Trump held a summit with Chinese President Xi Jinping earlier this month, and has praised China's turning back of North Korean coal ships as a "big step" forward in the effort to enlist Chinese pressure on Pyongyang.
Pence said Monday Trump was "very hopeful that China will take actions to bring about a change of policy in North Korea," but added later that Washington was "troubled by China's economic retaliation against South Korea
(for) taking appropriate measures to defend itself" by deploying the US THAAD missile defense system.
Chinese Ministry of Foreign Affairs spokesman Lu Kang said Monday that Beijing's policy was "clear for all to see when it comes to promoting the denuclearization of the peninsula."
Lu said that prior to the THAAD deployment, relations between Beijing and Seoul were strong and "China didn't cause the current problem in bilateral ties."
Speaking Sunday, US national security adviser H. R. McMaster said the US hopes not to use military force but warned "this problem is coming to a head
McMaster said various US military and intelligence agencies are working on providing options to "have them ready" for Trump "if this pattern of destabilizing behavior continues."
On Friday, North Korea said the dangerous security situation was due to the "Trump administration's reckless military provocation."
"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.
Pence's visit to South Korea comes as the country prepares for an election next month following the ouster of President Park Geun-hye
Speaking alongside acting-President Hwang Kyo-ahn in Seoul, Pence commended him for his "steady hand in this time of transition in South Korea."
"Whatever change happens in your elections the commitment of the US to South Korea's safety and security will remain unchanged," Pence said. "We are with you 100%."
The election is expected to see South Korea swing to the left
and away from the conservative policies of Park's party.
The left-wing Democratic United Party has been critical of the deployment of THAAD and called for more engagement with North Korea to prevent further nuclearization.
Jean Lee, a global fellow at the US-based Wilson Center, said the next president "will have a lot of bearing on what kind of policy South Korea develops towards North Korea."
"(The election) could lead to a shift in alliances, shift in policy among South Korea, the US and Japan when it comes to" dealing with Pyongyang, she said.
Show of force
Pence's visit followed an impressive parade Saturday to mark the "Day of the Sun," the most important day in the North Korean calendar, when Pyongyang showed off an array of new missiles and launchers
Pyongyang paraded two new intercontinental ballistic missile-sized canisters as well as displaying its submarine-launched ballistic missile and a land-based version of the same for the first time, according to analysts.
The regime followed that with an attempted missile test Sunday from the eastern port of Sinpo. If that test leads to a nuclear test or an ICBM launch, there would be "a powerful punishing measure that North Korean authority can't endure," South Korean officials said.
US officials told CNN they did not believe the missile had intercontinental capabilities, and blew up almost immediately after launch.