Pence said the Trump administration wants to persuade North Korea to abandon its nuclear weapons “through peaceful means,” but he repeated the administration’s warning that “all options are on the table.”
In Washington, President Trump told CNN at the annual White House Easter Egg Roll that North Korea has “got to behave.”
White House press secretary Sean Spicer said that Trump would not be “drawing red lines in the sand” with North Korea.
Members of President Trump’s administration: Moments that made headlines
“He holds his cards close to the vest, and I think you’re not going to see him telegraphing how he’s going to respond to any military or other situation going forward,” Spicer said. “I think that the action that he took in Syria shows that when appropriate, this president will take decisive action.”
Spicer later cautioned reporters not to “make too much” of an analogy between Syria and North Korea.
A State Department official said Monday that the United States will continue trying to further isolate North Korea economically, politically and diplomatically.
The pressure will keep ratcheting up until Pyongyang stops conducting missile tests and demonstrates that it is willing to engage in negotiations, said Susan Thornton, the acting assistant secretary for East Asian and Pacific affairs.
“We’re looking for some kind of signal that they realize the current status quo is unsustainable,” she said. “They have to make a final decision about getting rid of illegal programs in order to turn the page and have a more normal relationship with the international community.”
“We have not seen that signal,” she added.
Pence arrived in South Korea just hours after North Korea launched its latest ballistic missile — which exploded within a few seconds — and amid a weekend of fanfare in North Korea, during which the regime showed off what appeared to be new missiles designed to reach the United States.
There, during a trip to the demilitarized zone between North and South Korea and later in remarks to journalists, he issued strong warnings to Pyongyang.
“Just in the past two weeks, the world witnessed the strength and resolve of our new president in actions taken in Syria and Afghanistan,” Pence said after delivering a statement to the news media alongside Hwang Kyo-ahn, South Korea’s acting president. Neither took questions.
“North Korea would do well not to test his resolve or the strength of the armed forces of the United States in this region,” Pence said.
Earlier this month, on Trump's command, the U.S. military launched 59 cruise missiles at a Syrian military airfield in retaliation for a chemical attack that killed scores of civilians.
Then, less than a week later, the U.S. military dropped a 22,000-pound bomb — the largest non-nuclear bomb ever used in combat by the United States — on Islamic State forces in eastern Afghanistan.
With Kim Jong Un’s regime conducting a steady stream of ballistic missile launches and signs of activity around its nuclear test site, the Trump administration has raised the rhetoric on possible military action to stop it in its tracks.
But any strikes against the North would probably bring the United States into a diplomatic crisis with China, the North’s main economic lifeline.
In Beijing, Foreign Ministry spokesman Lu Kang called for international talks with North Korea to ease tensions.
Russia, too, warned that the Trump administration was on what Foreign Minister Sergei Lavrov called a “very risky path.”
"I hope there will be no unilateral actions like those we saw recently in Syria," Lavrov told reporters in Moscow.
Both Secretary of State Rex Tillerson, who visited South Korea last month, and Pence have stated that "strategic patience" — the Obama-era policy of putting pressure on North Korea and waiting for it to return to negotiations — is over and that military action is an option to make North Korea desist.
The U.S. Navy's decision to reroute an aircraft carrier strike group destined for Australia to the "western Pacific" sparked speculation it was heading to the Korean Peninsula, adding to the jitters in the region.
The strike group left Singapore on April 8. Photos released by the Navy on Saturday showed that the carrier passed north through the Sunda Strait, the passage between the Indonesian islands of Sumatra and Java — about 3,500 miles from the Korean Peninsula, Defense News reported.
The Navy declined to give The Washington Post a more precise location than the “western Pacific” except to rule out the waters around South Korea or Japan.
“As our secretary of defense made clear here in South Korea not that long ago,” Pence said Monday, “we will defeat any attack, and we will meet any use of conventional or nuclear weapons with an overwhelming and effective response.”
Defense Secretary Jim Mattis visited Seoul in February.
Hwang, the acting president until the election to replace Park Geun-hye, said South Korea would "ensure the early deployment and operation" of an American-backed anti-ballistic missile system called Terminal High Altitude Area Defense (THAAD).
The plan has been controversial in South Korea, with some worried that it would make the South more of a target for North Korean missiles and others concerned about economic revenge being exacted by China.
The front-runner to replace Park in a snap presidential election to be held May 9, progressive politician Moon Jae-in, has promised to review the previous government's decision to host THAAD.
Beijing strongly objects to the antimissile system because it worries that the United States will use its batteries’ associated radar to snoop on China. China has imposed a painful economic boycott on South Korean exports and is making life difficult for South Korean companies in China.
Pence said the United States will press ahead with the THAAD deployment and chastised China for its efforts to put pressure on South Korea to change its mind.
“The United States is troubled by China’s economic retaliation against South Korea for taking appropriate steps to defend itself,” he said. “The better path would be for China to address the North Korean threat that is actually making such defensive measures necessary.
“While issues like [THAAD] remain, the president and I have great confidence that China will properly deal with North Korea, but as President Trump made clear just a few short days ago, if China is unable to deal with North Korea, the United States and our allies will,” the vice president said.
Carol Morello, John Wagner and Brian Murphy in Washington contributed to this report.