TOKYO — Vice President Mike Pence said the Trump administration plans to roll out its harshest sanctions yet against North Korea during a Wednesday news conference in Japan."I’m announcing that the United States of America will soon unveil the toughest and most aggressive round of economic sanctions on North Korea ever - and we will continue to isolate North Korea until it abandons its nuclear and ballistic missile programs once and for all," Pence said, speaking alongside Japanese Prime Minister Shinzo Abe at his official residence.The vice president offered no specific details of the sanctions, which his staff said the Treasury Department would officially unveil in the coming days.Pence made his comments during his first stop, in Japan, on a five-day trip through Asia intended to pressure Kim Jong Un’s regime to move toward denuclearization. He heads Thursday to South Korea, where he plans to meet with the South Korean President Moon Jae-in, as well attend the 2018 Winter Olympics in Pyeongchang - in an effort to counter North Korean propaganda.Pence has invited Fred Warmbier — father of Otto Warmbier, the American student who was sentenced to 15 years of hard labor while visiting North Korea and ultimately died upon his return to the United States — to attend the opening ceremonies of the Games with him Friday evening.The sanctions announced Wednesday mark Pence’s strongest tangible actions against North Korea on this trip so far."Last November as well, our administration re-designated North Korea as a state sponsor of terror," Pence said. "Together with Japan, and all our allies, let the world know this: We will continue to intensify our maximum pressure campaign until North Korea takes concrete steps toward complete, verifiable, and irreversible denuclearization."The Trump administration has been pursuing a "maximum pressure" approach, aiming to inflict so much economic pain on North Korea that Kim’s regime has no choice but to return to negotiations about its nuclear program.Kim admitted in his New Year’s address that the sanctions were causing "difficult living conditions," but has repeatedly vowed to withstand the U.S.-led pressure, and his regime so far has showed no signs of buckling.The Trump administration has already imposed round after round of direct sanctions on North Korea, while simultaneously leading efforts through the United Nations to cut off North Korea’s ability to earn money in the outside world.Pence’s hardline remarks Wednesday amounted to a "frontal assault" on South Korean President Moon Jae-in, said David Straub, a former State Department official who is now Sejong-LS Fellow at the Sejong Institute think tank near Seoul."We’ve seen some of these elements before but to put them all together in one place and deliver them standing beside Prime Minister Abe in Japan constitutes a frontal assault on Moon’s North Korea policy," Straub said. "They’re in total disagreement."While the Trump administration and Abe’s government have taken an increasingly tough approach toward Pyongyang and condemned the regime in unwavering terms, Moon has been much more conciliatory.Moon comes from the "sunshine policy" school of thought in South Korea. The policy got its name from an Aesop fable in which the wind and the sun compete to make a traveler take off his coat. The sun gently warms the traveler and succeeds - the moral of the fable being that gentle persuasion works better than force.But Moon’s government has attempted to paper over those differences, with the president repeatedly saying he supports "maximum pressure" even as he asked North Korea for direct talks and raised the idea of resuming joint economic projects.Pence starkly laid bare those divisions, though it was also the timing and location of his remarks that astounded Straub, who wrote a book about the U.S.-South Korea alliance."It’s been clear that there are gaps, but they have made an effort to praise each other," Straub said. "This speech makes those disagreements blindingly obvious."Indeed, Pence’s remarks came barely an hour after South Korea’s unification ministry announced that Kim Jong Un planned to send his sister, Kim Yo Jong, as part of the North’s high-level delegation to the Olympic Games. She will become the first member of the North’s ruling family to ever visit the South.Pyongyang had already announced that it would send Kim Yong Nam, who is constitutionally North Korea’s head of state, but government officials were hoping that Kim Yo Jong would also attend.She has a position on the powerful political bureau of the ruling Workers’ Party and is a close adviser to her brother. She is someone that can deliver a message to Kim Jong Un, and the South Korean government is expected to go out of its way to accommodate her.Pence’s sanctions announcement Wednesday further complicates that dynamic.Previously, "smart sanctions" had targeted North Korea’s ability to acquire parts or funding for its nuclear and missile programs. But over the last six months, the sanctions have come to look more like a general trade embargo.Multilateral sanctions have cut mineral, garment and seafood exports, which had accounted for about one-third of the country’s $3 billion annual export revenue. They also prohibited U.N. member states from accepting workers sent by the North Korean regime, which had been bringing in an estimated $500 million a year for Kim’s coffers.All the sanctions require the cooperation of China and, to a lesser extent, Russia, which are both veto-wielding permanent members of the Security Council and both share borders with North Korea.Beijing, even while supporting sanctions resolutions in the past, has been reluctant to fully implement them for fear of causing the regime to collapse. That would likely lead to millions of hungry North Koreans flooding across its north-eastern border, and to American troops being able to move up the Korean Peninsula to the Chinese border.But there have been signs in the last six months that China is seriously cracking down on North Korea, with workers in Chinese factories being sent home and cargo being subjected to stringent inspections.Still, Russian President Vladimir Putin has publicly doubted is the utility of the sanctions, calling them "useless" and saying North Koreans would "rather eat grass than give up their nuclear program."However, the Japanese prime minister, who is both a staunch supporter of President Trump and a fierce critic of the North Korean regime, has supported Washington’s hardline approach, even as there are few, if any, direct measures that Tokyo can take to inflict direct pain on Pyongyang.Speaking with Abe Wednesday, Pence made clear that the Trump administration values its "strong partnership" with Japan, and is eager to further fortify that bond to confront "the menace and threat from the regime in North Korea."In the news conference, Pence reiterated his administration’s hardline against North Korea, as well as its commitment to the safety and security of the Japanese people."The era of strategic patience is over," he said. "All options are on the table, and the United States has deployed some of our most advanced military assets to Japan and the wider region, to protect our homeland and our allies."