Iran's Supreme National Security Council Secretary and chief nuclear negotiator Saeed Jalili answers a question during a final news conference in Almaty on Feb. 27, 2013. (Pavel Mikheyev/Associated Press)

Prospects for a nuclear deal with Iran received an unexpected boost Wednesday when negotiators from Tehran and six world powers emerged from talks with a commodity rarely seen in recent Iranian diplomacy: optimism.

Two days of negotiations in Almaty, Kazakhstan, yielded little tangible progress other than a commitment to hold more talks in the coming weeks. But both sides described an improved atmosphere and an apparent softening of bargaining positions, leading a senior Iranian official to hail a possible “turning point” in the decade-long effort to resolve the nuclear crisis.

Western and Iranian officials acknowledged that formidable obstacles still exist, including over the specific steps Tehran must take to allay concerns about its pursuit of nuclear technology. U.S. officials also noted that Iran has sought to prolong negotiations in the past as a stalling tactic.

Still, a senior U.S. official at the Almaty talks said the Iranian team “appeared to listen carefully” to new proposals for ending the nuclear impasse. The official also said Tehran was unusually forthright in agreeing to a quick succession of follow-up talks, including technical consultations in March and a new round of formal negotiations in early April, again in Kazakhstan.

“Almaty was a useful step in the process,” said the official, who insisted on anonymity in discussing sensitive diplomacy.

Secretary of State John F. Kerry also called the talks “useful” and said the progress in Almaty could “pave the way for negotiations that lead toward a longer-term and more comprehensive agreement.” He reiterated his offer to hold bilateral talks with the Islamic republic.

“We’d like to move to a better relationship, and it begins with resolving this nuclear issue,” Kerry told reporters in Paris, where he was in the midstpart of a nine-nation trip.

The talks were the first in nearly eight months between Iran and the six-nation bloc known as the P5-plus-1 — the United States, Britain, China, Germany, France and Russia. The negotiators met against a backdrop of Western anxiety over Iran’s recent steps to boost its output of enriched uranium, which can be used to fuel nuclear power plants or, with additional processing, to form the explosive core of a nuclear weapon.

The negotiations began Tuesday and were expected to last one day, but a second day was added as diplomats traded proposals for addressing international anxieties over Iran’s nuclear program.

U.S. diplomats described the outlines of a new offer to Iran that would ease some of the pain from economic sanctions in exchange for specific cuts and restrictions to its nuclear program. Under the proposal, Iran would freeze production of a more highly enriched form of uranium that can be quickly converted for use in a weapons program. It would also have to agree to more intrusive inspections of its nuclear facilities and to halt uranium enrichment at Fordow, a plant built inside a mountain near the city of Qom.

Iran has balked at such demands in the past. In an attempt to overcome Iran’s resistance, the new proposal would provide immediate relief from some specific sanctions. Western diplomats declined to describe the proposed sanctions relief but said Iran would continue to face banking sanctions and an oil embargo, at least in the short run.

“The sanctions-easing steps contained in the Almaty proposal are meaningful and would be of substantial benefit to Iran,” the senior U.S. official said. The official added that the Iranian team “indicated that a number of the ideas contained in the proposal merited further consideration.”

After the talks ended, Iran’s chief negotiator, Saeed Jalili, cautioned that there remains “a long distance to the desirable point,” particularly on the issue of proposed limits to Iran’s uranium-enrichment program. But he said the atmosphere had changed markedly since the last attempt at negotiations failed eight months ago in Moscow.

“Despite the behavior that they have shown over the past eight months, it was they who tried to get closer to our point of view,” Jalili told reporters in Almaty. “We see that as a positive step. If they are really changing their approach, and if they are approaching the talks with a strategy to get closer to mutual cooperation, this could be a turning point.”“While an agreement to meet again may not impress skeptics of diplomacy,” Parsi said, “an important development did occur: The parties began searching for a solution.”

Current and former U.S. officials and arms-control experts generally welcomed the news of progress at Almaty, noting that the modest achievement exceeded the low expectations.

“Given the circumstances, this was the best likely outcome,” said Trita Parsi, president of the National Iranian American Council and author of “A Single Roll of the Dice,” a book on the Obama administration’s troubled history of engagement with Iran.

Rezaian reported from Tehran. Anne Gearan in Rome contributed to this report.