President Donald Trump reinserted himself into the Iran nuclear negotiations this week, with decidedly mixed results.

Trump’s reiteration Tuesday that he isn’t looking for regime change was welcome. As efforts to persuade Iran to scale back uranium enrichment intensify, it’s important for the regime to know that it faces no existential threat. The U.S. hopes only to crimp its capacity to menace its neighbors and disrupt the world economy. If Iran reins in its destabilizing activities — promoting terrorism, arming proxy militias, pursuing ballistic missiles and so on — the U.S. would be content to live and let live, as it does with other authoritarian governments.

Unfortunately, a second assertion by the president will make such a detente much harder. In recent weeks, the administration has unwisely signaled an eagerness to make a deal with Iran, as long as it forswears nuclear weapons. After Secretary of State Mike Pompeo hinted on Tuesday that the regime was newly open to negotiations, Trump seemed to double down: “They’d like to talk,” he said, “and we’ll see what happens.”

This is at best naïve and at worst disingenuous. There’s no excuse for misreading the messages from Iran. Supreme Leader Ali Khamenei has stated repeatedly that he has no interest in talks. He flatly refused a good-faith offer of mediation from Japanese Prime Minister Shinzo Abe. French and German envoys dispatched to Tehran have met with no more success. Even Pompeo’s hopeful remarks were shot down by the Iranians within hours.

Such rhetoric is increasingly being matched with action. Iran’s decision to ratchet up uranium enrichment, as well as a flurry of attacks on tankers and oil installations in its neighborhood, suggests the regime is hoping to intimidate Trump into easing up on sanctions or offering other concessions.

The president can’t give in to such threats. Sanctions are a long game, and it’s essential now to show resolve.

Before any resumption in negotiations, Iran needs to demonstrate that it is mending its ways. Freezing uranium enrichment should be a minimum requirement. The regime must also show a willingness to end its malign activities in the region. A good place to start would be Yemen, where the conflict between Iranian-backed Houthi rebels and an Arab coalition has reached an impasse. The decision of the United Arab Emirates to withdraw its troops provides an opportunity for Iran to make a reciprocal gesture.

Trump, for his part, could help by clarifying what his objectives are, specifying what preconditions his administration is setting for the resumption of talks, and better coordinating his efforts with America’s European allies. A united front, pursuing achievable goals, would be far more effective than the administration’s current ad hoc diplomacy.

Sending mixed signals, as Trump did this week, will only increase the risk of confusion, miscalculation or worse.

Editorial by Bloomberg