SECRETARY OF State Rex Tillerson is being faulted for undiplomatic speaking during his tour of Asia over the weekend. Among other things, he parroted official Chinese rhetoric about “mutual respect” and “win-win solutions,” which Beijing hailed as deferral to its uncompromising positions on matters such as Taiwan. Perhaps Mr. Tillerson was suffering from a lack of seasoned staff. Or perhaps he was offering “face” to Chinese President Xi Jinping to compensate for vigorous private arm-twisting on the principal subject of the tour, North Korea.

We are cautiously willing to bet on the latter. Though many of its early foreign policy actions have been inept or incoherent, the Trump administration appears to have properly focused on what may be the biggest single threat it inherited: the manic pursuit by the regime of Kim Jong Un of nuclear warheads and the capacity to launch them at the continental United States. Since President Trump took office, Pyongyang has conducted two tests of missiles and another of a rocket engine that might be used on an intercontinental ballistic missile. It is rapidly stockpiling nuclear warheads. And the 30-something Mr. Kim has demonstrated his capacity for reckless aggression by, among other things, reportedly orchestrating the murder of his half brother at an international airport in Malaysia.

The Obama administration’s strategy toward North Korea — “strategic patience” — amounted to ignoring the gathering threat. But the outgoing president appears to have warned his successor about the problem in their first post-election meeting — and Mr. Trump seems to have listened. During his trip to Japan, South Korea and China, Mr. Tillerson bluntly declared that “the policy of strategic patience has ended” and that “we are exploring a new range of diplomatic, security and economic measures” — including possible military action.

No doubt the administration is discovering what deterred President Barack Obama: U.S. options range from the very bad to the truly terrible. A military strike on North Korea’s nuclear or missile facilities might not succeed while triggering a potentially catastrophic war — though, as Mr. Tillerson hinted, further steps by North Korea toward deploying nuclear-armed ICBMs might compel such action. Tougher sanctions might impose terrible hardship on North Korea’s people without altering the course of a regime that has allowed millions to starve to death. Renewing negotiations with Pyongyang risks repeating the futile exercises of the past two decades, when North Korea pocketed U.S. aid and political concessions while violating its promises to freeze nuclear work.

Judging from Mr. Tillerson’s public comments, the new administration is starting with the most sensible opening steps — a strong effort to enlist China, as well as other nations, in a new campaign of pressure. He said, “I don’t believe we have ever fully achieved the maximum level of action that can be taken” under existing U.N. Security Council resolutions — and he’s right. Chinese banks continue to help North Korea trade in U.S. dollars, as do the regime’s own shell companies. Chinese companies continue to supply North Korea with not only food and energy, but also materials Pyongyang can use to build bombs.

What has not been tried on North Korea is the full-court economic press that was applied to Iran. In this case, it may not succeed in inducing the regime to check its nuclear ambitions. But it is the right place to start.