The United States would propose a resolution “to update and strengthen” U.N. sanctions in response to North Korea’s “increasingly dangerous provocations,” U.S. ambassador to the United Nations Linda Thomas-Greenfield said Friday. North Korea confirmed Thursday that it test-fired its biggest-yet intercontinental ballistic missile, Hwasong-17, as leader Kim Jong-un ordered the hermit nation to prepare for a “long-term confrontation” with the United States. Speaking at a U.N. Security Council briefing, Thomas-Greenfield said that the launch posed a threat to the entire international community and warrants “an immediate response” from the council. “It is clear that remaining silent—in the hope that the DPRK would similarly show restraint—is a failed strategy. We must pivot to a successful one,” she said, using the official acronym for North Korea. Thomas-Greenfield said that Washington would propose a resolution to tighten Security Council sanctions against North Korea, though she did not specify what the new sanctions would …