Negotiators for the U.S. and Iran, working to revive an international deal aimed at restricting Tehran’s atomic ambitions, are looking for ways to untangle a knot of interlocking American sanctions in exchange for Tehran’s return to limits on its nuclear activities. After former President Trump pulled out of the agreement in 2018, saying it didn’t go far enough, Washington reimposed sanctions lifted under the deal and imposed a raft of new ones. Some are related to Iran’s nuclear program; others target alleged human-rights abuses and terrorism as well as Tehran’s work on ballistic missiles.

In response, Iran began to roll back limits on uranium enrichment and other activities that were part of the 2015 accord, formally known as the Joint Comprehensive Plan of Action, or JCPOA. Diplomats are trying to chart a course toward lifting of sanctions that have battered the Iranian economy with commensurate steps from Iran’s side.

Representatives of the European Union, Iran and others attended the Iran nuclear talks Thursday in Vienna.

Iranian officials have said they want all the Trump-era sanctions removed before it returns to complying with the nuclear deal. “Anything imposed by the Trump administration should be lifted,” before Iran makes any concessions, Iranian chief nuclear negotiator Abbas Araghchi said in an interview last week. The Biden administration has said it is willing to lift all sanctions that are “inconsistent” with the nuclear deal, but hasn’t identified those it will leave in place. Biden administration officials have said that they intend to retain some sanctions imposed on human rights, ballistic missile and terrorism grounds and may impose new ones. They say that the 2015 deal doesn’t preclude such actions.

Iran showed the first indication Thursday that it might be willing to compromise on its stance, which has been firm for months. Mr. Araghchi in an interview in Vienna said the parties would now begin the practical work of preparing a list of sanctions the U.S. was willing to lift, and the reciprocal actions Iran would take.

“There is room to negotiate how to identify sanctions, which [sanctions] should be lifted, but our position is quite clear,” he said. “As far as we are concerned, all sanctions imposed or reimposed or relabeled by the Trump administration are JCPOA-related and should be lifted,” he added.

“Of course, there are different ways to see that, and that’s why we negotiate.”