UNITED NATIONS -- U.S. and European diplomats said Thursday they were pleased by a new tone and attitude from Iran in talks aimed at resolving the impasse over its nuclear program. They set a new round of negotiations for next month.
After a group meeting and then a one-on-one session between Secretary of State John Kerry and Iranian Foreign Minister Mohammad Javad Zarif, Kerry called the talks "constructive" and said he was struck by a "very different tone" from Iran. But he stressed that words must be translated into action if Iran wants to prove it is not seeking to develop a nuclear weapon.
"We've agreed to try to continue a process that would try to make concrete and find a way to answer the questions that people have about Iran's nuclear program," Kerry told reporters. "Needless to say, one meeting and a change in tone, that was welcome, does not answer those questions."
"All of us were pleased that the foreign minister came today and that he did put some possibilities on the table,'' he said.
The meeting between Zarif and Kerry, who sat next to each other at a U-shaped table, was the highest-level direct contact between the United States and Iran in six years. EU foreign policy chief Catherine Ashton suggested that the two men had shaken hands and been cordial with each other.
Ashton called the meeting "substantial" and announced that the parties had agreed to "go forward with an ambitious timeframe." The next step will be a meeting of senior negotiators in Geneva on Oct 15-16, she said.
Speaking after Kerry, Zarif said the meetings had been "very constructive" and "very businesslike."
"We hope to be able to make progress to solve this issue in a timely fashion (and) to make sure (there is) no concern that Iran's program is anything but peaceful," he said.
"I am satisfied with this first step," Zarif said. "Now we have to see whether we can match our positive words with serious deeds so we can move forward."
He said the result would have to include "a total lifting" of the international sanctions that have devastated Iran's economy.
British Foreign Secretary William Hague said there had been a "big improvement in the tone and spirit" from the top Iranian diplomat compared with representatives of the previous Iranian government.
German Foreign Minister Guido Westerwelle said the meeting had taken place in a "completely different tone, atmosphere and spirit" that what the group was used to and that a "window of opportunity has opened" for a peaceful resolution of the situation. He warned, though, that Iran's words would have to be matched by actions.
"Words are not enough," he said. "Actions and tangible results are what counts. The devil is in the detail, so it is now important that we have substantial and serious negotiations very soon."
The meeting on the sidelines of the U.N. General Assembly marked the highest-level direct contact between the United States and Iran in six years.
In Washington before the meeting, the White House resisted putting a timeline on the nuclear negotiations.
"We're not expecting any breakthrough in this initial meeting," said White House spokesman Jay Carney. "But this is part of us testing the seriousness of the Iranians, who are obviously engaging in new overtures and showing new interest in trying to solve this very serious matter."
Encouraged by signs that Rouhani will adopt a more moderate stance than his predecessor Mahmoud Ahmadinejad, but skeptical that the country's all-powerful supreme leader will allow a change in course, President Obama has directed Kerry to lead a new outreach and explore possibilities for resolving the long-standing dispute.
Rouhani's pronouncements at the U.N. have raised guarded hopes that progress might be possible. But they have also served as a reminder that the path to that progress will not be quick or easy.
In his speech to world leaders at the U.N. on Tuesday, he repeated Iran's long-standing demand that any nuclear agreement must recognize the country's right under international treaties to continue enriching uranium.
Rouhani said earlier Thursday that all nations including Israel should dismantle their nuclear weapons, words that were taken as introducing obstacles to a nuclear deal.
Those comments show that Rouhani is not serious, Michael Rubin, a former Middle East expert at the Pentagon under former-President George W. Bush, asserted.
"The more you complicate the issue the more you're setting up the talks to fail," Rubin said.
Michael Doran, a former Middle East adviser in the Bush White House, said Rouhani's words about Israel are "a wise negotiating strategy" to present Iran as a victim of a Western double standard and attempt to change the subject from its own weapons.
U.S. negotiators should define "a speedy and meaningful process by which the Iranians would have to talk about brass tacks very quickly," Doran said. "The Iranian strategy will be to put all kinds of other things on the table other than reprocessing" of uranium fuel.
Rouhani's chief goal is to seek a speedy lifting of sanctions that have squeezed the Iranian economy, and which many analysts say have brought Rouhani to the negotiating table.
"I would hope the Americans will not fall for that," Doran said.
After addressing he Council on Foreign Relations, Rouhani took a question about how many centrifuges would be needed for what he says is a peaceful nuclear program, The question has also been raised by analysts who fear the industrial-level nuclear fuel production that Iran has built will allow it to produce enough highly-enriched uranium for weapons.
Rouhani's dodged the issue by directing his questioner to the web site of the United Nations nuclear watchdog, the International Atomic Energy Agency. "I don't think the actual number will mean much to our listeners," he said.
Contributing: Oren Dorell,in Washington; William M. Welch in Los Angeles; Associated Press.