After a meeting with Iranian officials on the sidelines of the United Nations General Assembly Wednesday evening, Secretary of State Rex Tillerson informed reporters that President Donald Trump was “still considering” whether to decertify Iran’s compliance with the nuclear deal.

But he was wrong.

Just a few hours earlier, Trump told reporters that he had made up his mind on the matter. “I have decided,” Trump said to a group of reporters following a meeting with Palestinian Authority President Mahmoud Abbas in New York. He repeated that statement two more times, though he refused to say what his decision was. He merely teased: “I’ll let you know what the decision is.”

A journalist quickly corrected Tillerson on the spot. As the Washington Post reports, the secretary of state appeared “sheepish” about the error, and stumbled while trying to regain composure.

"I didn't know he was going to say today he made a decision," Tillerson said. Then he added, "I knew he had, but I didn’t know he was going to say he had."

This is a bad look for the administration — and it reveals a problem that goes much deeper than just the embarrassing spectacle of being corrected by a reporter about your administration’s policies in front of foreign officials.

The big issue with the Tillerson-Trump disconnect is that it exacts a toll on Tillerson’s credibility as the nation’s top diplomat. If Tillerson isn’t privy to the latest news about where the president stands on one of the most contentious foreign policy issues of the day, then how can he be an effective emissary on the president’s behalf?

Tillerson was speaking to reporters right after emerging from a private meeting with Iranian officials. We don’t know exactly what was discussed, but if he tried to use the idea that Trump was still undecided on the deal as leverage in negotiations with the Iranians, it probably wasn’t fruitful. Tillerson would have looked uninformed either during the meeting or after.

The Trump-Tillerson divergence also signals that something is awry on a systemic level. If the country’s top diplomat isn’t informed on the president’s stances on the issue, then what does that say about other lower-ranking officials who are involved in countless bilateral and multilateral meetings at the UN General Assembly? If foreign diplomats take them less seriously, it makes any discussion on issues from peacekeeping to trade to nuclear disarmament less productive.

This is far from the first time that Trump and Tillerson have appeared at odds. In the wake of the Saudi Arabia-led embargo of Qatar, for example, Tillerson tried to establish an air of calm and neutrality since both countries are US allies — only to be contradicted when Trump openly sided with Saudi against Qatar on Twitter and elsewhere. That kind of mixed signaling makes US policy look incoherent and makes diplomatic solutions harder to achieve.

There are signs that mixed signaling is occurring on Iran as well. The conventional wisdom among a number of Iran watchers in Washington is that Trump is likely to officially declare that Iran is not complying with the Iran deal, potentially setting off a process that would unravel the deal. And there are recent reports indicating that Trump may indeed do it. Yet the top general of US Strategic Command, Gen. John Hyten, said on Wednesday that Iran is adhering to the nuclear deal.

So what will happen next? Only Trump knows. I think.