TEHRAN, Iran — With a first round of nuclear negotiations with world powers ending without agreement, Iranian officials looked ahead Sunday to parallel talks with the U.N.’s nuclear chief amid reminders that concessions by Tehran have limits.

The overall message from Iran closely mirrored the work-in-progress tone of U.S. Secretary of State John Kerry and other powerful envoys, who failed to seal a first-step accord during overtime talks in Geneva but then quickly agreed to try again next week.

The administration of Iranian President Hassan Rouhani is emphasizing that the talks are a work in progress. He’s mollifying hard-liners by reasserting that Iran will keep on with nuclear activities that it insists are its right, but at the same time is trying to quell any hints of stalemate in the negotiations. The impression that the talks are sputtering could embolden critics uneasy over his government’s historic outreach to the U.S and fast-track effort to ease Western concerns over Tehran’s nuclear ambitions.

The framework for a possible deal could see an easing of U.S.-led economic sanctions in exchange for curbs on Iran’s highest levels on uranium enrichment. Among the complications ahead, though, is addressing French concerns that the proposed limits on Iran’s ability to make nuclear fuel don’t go far enough and alarm over a planned heavy water reactor that produces greater amounts of byproduct plutonium, which can be used in nuclear weapon production.

Iran insists it rejects nuclear arms and only wants reactors of energy and medical applications, such as isotopes for cancer treatment.

Rouhani said progress was made during “serious” talks in Geneva with the six-nation group, the permanent U.N. Security Council members plus Germany.

But he repeated that Iran cannot be pushed to fully give up uranium enrichment — a comment that echoes past declarations and appears aimed at opponents of his nuclear dialogue with the West.

In related talks, U.N. nuclear chief Yukiya Amano headed to Tehran on Sunday for meetings on the practical aspects of expanding international monitoring and gaining greater access to nuclear sites. Attempts have been stymied by nearly two years of arguments over what can be seen and who can be interviewed by experts from the U.N.’s International Atomic Energy Agency.

Iran’s new leadership has promised more cooperation, and Amano said “we aim to build” on the offers. A positive report from Amano could help drive forward negotiations set to resume Nov. 20 between Iran and the six world powers.

Foreign Minister Mohammad Javad Zarif, in a posting on his Facebook page Sunday, said there are “some problems” still to overcome with the six powers, but called the latest round “serious but respectful.” Abbas Araghchi, Iran’s deputy foreign minister and one of the top nuclear negotiators, call the Geneva rounds “very intensive and difficult, but useful and constructive.”

The West and its allies fear Iran’s uranium enrichment labs could one day produce weapons-grade material. But, in an important shift, the U.S. and others no longer appear to demand a complete halt to enrichment and are concentrating on curbing the highest-level production, currently at 20 percent. Such material is needed for Iran’s lone research reactor, which makes isotopes for medical treatments, but is only just several steps away from warhead level at more than 90 percent enrichment. Energy-producing reactors use uranium enriched at levels of about 3.5 percent.

In an address to parliament, Rouhani said uranium enrichment is a “red line” that cannot be crossed.

“Nuclear rights in the international framework, including uranium enrichment, on its soil” are not negotiable, Rouhani was quoted as saying by the semiofficial ISNA news agency. “For us red lines are not crossable.”

Iran says it cannot be forced to give up enrichment because it has signed a U.N. treaty governing the spread of nuclear technology. The pact allows for enrichment under U.N. monitoring.

Israeli Prime Minister Benjamin Netanyahu has criticized what he considers readiness by the six powers to be too generous to Tehran for not enough in return. The U.S and others are considering easing economic sanctions in return for a possible suspension in 20 percent enrichment.

Speaking Sunday before a weekly cabinet meeting, Netanyahu said he had spoken over the weekend with the leaders of the U.S, Russia, France, Britain and Germany, pressing them to not reach a hasty deal.

“I asked them to delay and I’m glad they did. I do not fool myself — there will be an agreement. I hope it will not be an agreement at any price — a good one, not a bad one,” he said.

Kerry, who rushed to Geneva on Friday after the talks began to founder, said “significant progress” had been made on the remaining differences, but noted there were “certain issues that we needed to work through.”

Still, Kerry’s talks in Geneva were the longest high-level negotiations between Iran and the United States in decades — a sign of the improved atmosphere between the two countries since moderate-leaning Rouhani took office in August.

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Associated Press writers John Heilprin, George Jahn and Matthew Lee in Geneva, Jamey Keaten in Paris, Daniel Estrin in Jerusalem and Brian Murphy in Dubai, United Arab Emirates, contributed to this report.

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