April 16 (UPI) -- Vice President Mike Pence made an unannounced visit to the Demilitarized Zone separating North and South Korea on Monday, a day after calling North Korea's failed missile launch a "provocation."
The vice president said "all options are on the table" over North Korea's military threats, including Sunday's failed missile launch. He added that the alliance between South Korea and the United States is "ironclad."
Pence arrived in Seoul on Sunday for a 10-day tour of four Asian countries.
"This morning's provocation from the North is just the latest reminder of the risks each one of you face each and every day in the defense of the freedom of the people of South Korea and the defense of America in this part of the world," he said at an Easter dinner at Yongsan military base in Seoul.
Pence said he had spoken with President Donald Trump, who asked to convey to the troops in South Korea that "we're proud of you and we're grateful for your service."
Pence was departing from Alaska when North Korea launched a ballistic missile that exploded within a few seconds. 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.
A White House foreign policy adviser traveling with Pence on the plane said the United States did not need to take action "to reinforce [North Korea's] failure."
"If it had been a nuclear test then other actions would have been taken from the U.S.," the adviser told reporters on the vice president's plane.
National security adviser Lt. Gen. H.R. McMaster, who traveled to Afghanistan, said Sunday on ABC's This Week, "this problem is coming to a head. And so it's time for us to undertake all actions we can, short of a military option, to try to resolve this peacefully."
But the United States hopes not to use military force.
"The president has made clear that he will not accept the United States and its allies and partners in the region being under threat from this hostile regime with nuclear weapons. And so we're working together with our allies and partners, and with the Chinese leadership, to develop a range of options," McMaster said.
He added, "In the coming weeks, months, I think there's a great opportunity for all of us ... to take action short of armed conflict so we can avoid the worst."
The adviser traveling with Pence said Trump had numerous ways to respond if needed.
"We've got a range of options -- both militarily, diplomatic and others -- so we have a wide array of tools at disposal for the president should he choose to use them," the official said. "But for this particular case, if they took the time and energy to launch a missile that failed, we don't need to expend any resources against that."
The missile was probably a medium-range missile and not an intercontinental ballistic one, according to U.S. intelligence.
"We weren't surprised by it, we were anticipating it," the foreign policy adviser said. "It wasn't a matter of if, it was a matter of when. The good news is that after five seconds it fizzled out."
Pence was scheduled to meet with Hwang Kyo-ahn, the acting president of South Korea, on Monday to discuss the North Korean threat.
Trump is spending Easter weekend at his Mar-a-Lago estate in Palm Beach, Fla.
He didn't respond to the missile firing but posted on Twitter Sunday morning: "Why would I call China a currency manipulator when they are working with us on the North Korean problem? We will see what happens!"
One hour later he posted, "Our military is building and is rapidly becoming stronger than ever before. Frankly, we have no choice!"
Also Sunday, Secretary of State Rex Tillerson spoke by telephone with China's top diplomat, Yang Jiechi, and they "exchanged views on the current situation on the Korean Peninsula," China's Foreign Ministry said in a statement.