YOKOTA AIR BASE, Japan >> U.S. Vice President Mike Pence is pouring cold water on the warming ties between North and South Korea just as the two still-warring countries are joining up to compete together in the Winter Olympics.

Making his way to Pyeongchang to lead the U.S. delegation to Friday’s opening ceremonies, Pence has embarked on a set of symbolic visits designed to draw attention to the North’s terrible human rights record and nuclear aggression. With determined rhetoric — and the promise of more “aggressive” economic sanctions against the North — Pence is looking to refocus American allies on the North Korean threat.

“We will not allow North Korea to hide behind the Olympic banner the reality that they enslave their people and threaten the wider region,” Pence said today after meetings with Japanese Prime Minister Shinzo Abe in Tokyo.

Pence arrives in Seoul on Thursday for meetings with President Moon Jae-in just as South Korea seizes on the games for a diplomatic opening with the North, including the first visit of North Korea’s ruling family since the end of the 1950-53 Korean War. Aides say the vice president is advancing a counter message, using the games as an opportunity for the South and the broader international community to exert what President Donald Trump has termed “maximum pressure” against the North.

Before departing for Korea, Pence announced that the U.S. would unveil in coming days “the toughest and most aggressive round of economic sanctions on North Korea ever.”

He also ratcheted up his rhetoric on the North’s human rights abuses in a speech to U.S. service members at Yokota Air Base in Japan.

“As we speak, an estimated 100,000 North Korean citizens labor in modern-day gulags,” Pence said Thursday before departing Japan. “Those who dare raise their voices in dissent are imprisoned, tortured and even murdered, and their children and grandchildren are routinely punished for their family’s sins against the state.”

Pence toured joint U.S. and Japanese operations centers at the U.S. base that monitor and react to crises on the peninsula and the region at large. He told troops to “be vigilant,” warning against falling for the North’s diplomatic overtures. “We are ready for every eventuality,” he added.

Pence’s strenuous efforts to highlight the threat from the North and its treatment of its people present a dilemma for Moon. The South Korean leader has long advocated engagement with Pyongyang and sees the Olympics as an opportunity to quell tensions that have escalated over its nuclear program. He has limited room to maneuver as his guest from Washington strongly criticizes the North and emphasizes the need to crank up the pressure campaign.

U.S. officials declined to offer details on the expected new sanctions beyond Pence’s comments, citing concerns that any additional information could be used by those trying to skirt the new measures. They are expected to be implemented before the conclusion of the games.

North Korea already is facing unprecedented sanctions after three U.N. Security Council restrictions in the past year that have slashed the pariah nation’s export revenue and capped fuel imports. Unilaterally, the U.S. has also targeted North Korean shipping companies and Chinese trading networks. A potential escalation of sanctions could be the U.S. blacklisting Chinese banks accused of providing North Korea access to the international financial system and facilitating sanctions evasion.

Administration officials said they had long expected the North would seek to use the Olympics, taking place just 50 miles from the heavily-mined demilitarized zone, as an opportunity to put a softer face on the regime, and painted Pence’s visit as a counterbalance to those efforts. At the same time, the vice president has deliberately left the door open to a possible encounter with North Korean officials expected to be in attendance.

Today, the North announced that Kim Yo Jong, the sister of dictator Kim Jong-un, would attend the games, joining the country’s nominal head of state, Kim Yong Nam.

Pence pledged that his message in any potential interaction would include the same point he has been making publicly: that the North must renounce its nuclear weapon and missile programs.

In Washington, Defense Secretary Jim Mattis told reporters today that Pence is “quite capable of making the call” on whether to meet with North Korean officials at the Olympics. Asked if war with North Korea is closer than when Trump took office a year ago, Mattis said U.S. policy is “firmly in the diplomatic lane,” as shown by agreement among world powers to increase sanctions. He added that the policy is backed by “viable military options.”

Pence began his trip with a visit to Alaska, where he received a briefing on the U.S. missile defense system with U.S. Northern Command and highlighted the upcoming deployment of an additional 20 ground-based interceptors that will be ready to respond to a North Korean launch. In Japan, Pence watched Japanese troops demonstrate the simulated deployment of Japan’s surface-to-air missile defense system, which would attempt to intercept a North Korean missile. He also participated in a briefing at Japan’s Ministry of Defense on the threat.

Abe echoed Pence’s comments through a translator, urging countries “not to be lured by the charm offensive of North Korea.” Abe added that the U.S. and Japan are “100 percent on the same page” on North Korean policy. The U.S., Japan, and South Korea are set to hold trilateral talks later this week

In South Korea, Pence will meet Friday morning with North Korean defectors as he pays respects at the Cheonan Memorial in Seoul, which honors the 46 South Korean sailors killed in a 2010 torpedo attack attributed to the North.

Pence’s personal guest at the games will be Fred Warmbier, the father of Otto Warmbier, an American who died last year days after his release from captivity in North Korea.