ISTANBUL — Iran has agreed to return to nuclear negotiations in Vienna by the end of November, Tehran’s top negotiator said Wednesday, signaling the possible revival of a process aimed at restoring the 2015 nuclear deal that has been stalled for months and surrounded by uncertainty.

In a message posted on Twitter, the negotiator, Ali Bagheri, the deputy foreign minister, who has been meeting with European diplomats in Brussels, said the exact date of the negotiations would be announced next week.

Bagheri said he had engaged in “very serious and constructive dialogue” with Enrique Mora, the European Union’s deputy secretary general for political affairs, “on the essential elements for successful negotiations.” But Peter Stano, a foreign affairs spokesman for the European Union, said “there is nothing to announce at the moment.”

“We always announce any upcoming meeting in Vienna when appropriate,” he said.

Iran suspended the negotiations in June after the election of its new president, Ebrahim Raisi, a hard-line cleric who expressed a willingness to revive the nuclear deal, known as the Joint Comprehensive Plan of Action (JCPOA), but is wary of broader engagement with the West.

 For months, his government has said it would return to the negotiating table but declined to set a date, feeding a growing sense of pessimism and alarm over whether the restoration of the nuclear deal was possible.

President Donald Trump in 2018 withdrew the United States from the agreement, under which Iran agreed to limit its nuclear activities and submit to international monitoring in exchange for a lifting of U.S. and international economic sanctions. After Trump reimposed punitive sanctions, Iran restarted its high-level enrichment program.

President Biden promised to reenter the accord, and negotiations started in April. Iran refused direct talks with the United States, and European partners have acted as go-betweens for the two delegations.

Earlier this month, the Biden administration indicated it was shifting its stance toward the delayed resumption of the talks, from warning that the timeline was not infinite to saying it was prepared to consider what Secretary of State Antony Blinken called “other options if Iran does not change its course.”

Rafael Grossi, the director general of the International Atomic Energy Agency, said this month that because of interruptions in the agency’s monitoring of Iran’s nuclear activities, the next few weeks would be “decisive” in determining whether a resumption of negotiations was possible.

One deadline for returning to the talks was rapidly approaching: a meeting of the IAEA board of governors scheduled for mid-November. The European parties have repeatedly threatened to issue a condemnation of Iran and consider reimposing sanctions if it does not comply with verification commitments.

In a briefing published Wednesday, Henry Rome, a senior analyst on Iran at the Eurasia Group, said that Bagheri’s commitment to return to nuclear talks should “not be misinterpreted as a sign of real progress” and that the timing appeared to be a “tactical move to forestall a censure resolution” at the IAEA meeting in November.

“Iran’s other signals over the past few weeks have been decidedly negative, including its decision to back away from parts of a last-minute inspections deal and its reluctance to commit to pick up negotiations where they left off in June,” he wrote. He noted that Iran’s foreign minister said Wednesday that Tehran “accepted the format of the talks but hinted that the new government was unhappy with the status when they concluded.”

“The net result is that despite indicating it will return to talks, Iran’s positions at those talks are likely to reflect the hardline attitudes of the new government,” Rome wrote.

Quentin Aries in Brussels contributed to this report.