In Europe, officials do not believe the maximum pressure campaign has curbed Iran’s pursuit of a nuclear weapon.

One European diplomat said many Europeans remain concerned that the Trump administration is pursuing regime change — even though American officials insist that is not the goal. That diplomat added that, while the government in Tehran seemed shaken by the recent events, including the accidental downing of a Ukrainian airliner and the protests that followed, it is not likely to fall.

Nor do diplomats expect Iran to step back from its support for proxy militias or halt covert attacks. Arab states have warned of widening violence in the region if Tehran feels pushed too hard by the United States.

Anti-American sentiments in Iraq are already are on the rise, an American official said. A Middle East diplomat also predicted that Iran will carry out more attacks — similar to those against key oil fields in Saudi Arabia or oil tankers around the Strait of Hormuz — to test the Trump administration.

Even Senator Lindsey Graham, Republican of South Carolina and an Iran hawk, has recognized that the Trump administration is offering nothing to entice Iran to come to the negotiating table. Mr. Graham has told people he is working on potential inducements for Washington to offer Tehran.

New nuclear negotiations are unlikely soon.

Two senior Middle Eastern officials who speak to the Trump administration regularly on Iran said they do not expect Ayatollah Ali Khamenei, the supreme leader of Iran, to agree to start new negotiations with the United States soon. Instead, they said, he will wait to see the outcome of the American presidential election in November before deciding on a new strategy.

Mr. Trump said he wants to strike a new deal with Iran that is more expansive than the 2015 nuclear treaty that the Obama administration brokered with world powers and Tehran — and from which Mr. Trump withdrew the United States in 2018. Trump administration officials say they are looking not only for tougher restrictions on Iran’s nuclear program, but also for limits on its ballistic missile efforts and its support for regional militias.