International talks on Iran’s nuclear future ended on unexpectedly upbeat note on Wednesday, with Iran agreeing to further negotiations and hailing a possible “turning point” in the years-long diplomatic effort to resolve the nuclear crisis.

Negotiators from Iran and six world powers emerged from two days of private talks with cautious expressions of optimism and a commitment to holding additional meetings in quick succession in the coming weeks.

But officials also acknowledged significant differences over steps Iran must take to allay Western fears that Iran is secretly seeking to acquire nuclear weapons.

Iran’s chief negotiator Saeed Jalili, speaking to reporters after the end of the two-day session in Almaty, Kazakhstan, said his government had not yet seen an acceptable proposal that balanced Western demands for nuclear cutbacks with Iran’s desire for an easing of sanctions. 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 said. “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.”

Jalili also cautioned that there remains “a long distance to the desirable point,” particularly on resolving controversies over Iran’s uranium-enrichment program.

Secretary of State John F. Kerry, in Europe on his first overseas visit since his confirmation, also expressed cautious optimism about the outcome in Almaty.

“The talks were useful, and we look to Iran to carefully review the credible confidence-building steps that the P5-plus-1 have put on the table,” Kerry told reporters accompanying him on a flight to Paris. He was referring to the six-nation negotiating bloc, which includes the United States, Britain, China, Germany, France and Russia.

“If Iran engages seriously — and we hope they will — then these talks could pave the way for negotiations that lead toward a longer-term and more comprehensive agreement,” Kerry said.

European Union officials who led the P5-plus-1 delegation confirmed that the talks had yielded an agreement to hold two meetings in the coming weeks: a technical-level consultation in March, followed by a formal round of talks on April 5, again in Almaty.

Negotiators from Iran and the six world powers began meeting on Tuesday, then decided to add an unscheduled second day of talks as diplomats weighed competing plans for addressing international anxieties over Iran’s rapid gains in nuclear technology.

The extension came after a day of private exchanges that one Western diplomat characterized as “useful.” The United States and five other powers started the talks with a new proposal calling on Iran to give up parts of its nuclear program in exchange for partial relief from economic sanctions.

Iranian diplomats met for three hours Tuesday with delegates from the P5-plus-1, then conferred separately with leaders of several European delegations before resuming the discussions Wednesday morning.

The nuclear talks began amid low expectations, with U.S. and European officials expressing hope for modest momentum that eventually could lead to a comprehensive deal.

“We have come here with a revised offer, and we have come to engage with Iran in a meaningful way,” Catherine Ashton, the European Union’s representative at the talks, told reporters as the discussions began. “Our purpose [is] to make sure that we’ve had a good and detailed conversation, with the ambition that we see progress by the end of the meeting.”

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