“We look forward to working with them quickly and would expect that the U.N. sanctions will snap back into place,” he said on CNBC.

The Europeans’ decision to invoke the deal’s formal dispute resolution process arrived at a flammable moment for Iran, after weeks of domestic and international tumult. Antigovernment protests broke out in several cities last month, but the targeted killing by the United States of a top Iranian general this month temporarily united the country behind its leadership, and Iran fired missiles at bases housing American troops in Iraq in retaliation.

On Jan. 8, a Ukraine International Airlines flight to Kyiv crashed shortly after takeoff from Tehran, killing all 176 people aboard. After claiming for three days that the disaster had resulted from mechanical failure, Iran acknowledged that its own antiaircraft missiles had shot the plane down, as Western governments and news organizations had reported.

The crowds of mourners that packed Iranian cities for the slain Iranian commander, Maj. Gen. Qassim Suleimani, last week gave way to widespread, though smaller, protests against the government’s handling of the airliner accident.

The Iranian foreign minister, Mohammad Javad Zarif, acknowledged the protesters’ anger and seemed to validate it in remarks on Wednesday at a diplomatic conference in New Delhi.

“In the last few nights, we’ve had people in the streets of Tehran demonstrating against the fact that they were lied to for a couple of days,” news organizations reported him as saying.

After admitting to shooting down the plane, the Iranian military said that “human error” had been at fault, not any system problem. On Tuesday, the military’s Islamic Revolutionary Guards Corps said it had arrested a person who had recorded a video of a missile striking the plane — images that undermined Iran’s initial denials.