When Iran’s president and foreign minister arrived in New York a year ago for the opening of the United Nations General Assembly, they were riding high. At news conferences and in television appearances, they cast President Trump as an untrustworthy deal-breaker, and European leaders largely sided with the pair in a desperate effort to preserve the 2015 nuclear agreement after the United States renounced it.

This year could not be more different.

Suddenly, President Hassan Rouhani and his witty, often biting American-educated foreign minister, Mohammad Javad Zarif, are on the defensive. They are denying any Iranian involvement in the destruction of two major Saudi oil facilities, an assertion that even former Secretary of State John Kerry, who negotiated the nuclear accord four years ago and has become its biggest defender, finds far-fetched. Iran, he said, was behind the attack “one way or the other.”

Iran is now admitting how much damage the American-led sanctions have done to its economy — crashing the currency and turning a boomlet into a recession.

Mr. Zarif, while reserving most of his anger for Secretary of State Mike Pompeo, who he has called a “warmonger,” has now turned on the Europeans. After committing to preserving the nuclear deal by compensating for much of the revenue Iran was losing, the Europeans “have failed in every single one” of their specific commitments, he said in a meeting with reporters on Sunday.