U.S. Secretary of State John Kerry, left, and Iranian Foreign Minister Mohammad Javad Zarif attend a meeting of the five permanent members of the Security Council plus Germany during the 68th session of the United Nations General Assembly at U.N. headquarters, Wednesday, Sept. Iranian President Hassan Rouhani walks through the hallway during the 68th session of the General Assembly at United Nations headquarters, Thursday, Sept. Iranian President Hassan Rouhani speaks at a meeting on nuclear disarmament during the 68th session of the General Assembly at United Nations headquarters, Thursday, Sept. Iranian President Hassan Rouhani, center, walks through the hallway during the 68th session of the General Assembly at United Nations headquarters, Thursday, Sept. Iranian President Hassan Rouhani leaves the podium after speaking at a meeting on nuclear disarmament during the 68th session of the General Assembly at United Nations headquarters, Thursday, Sept. UNITED NATIONS (AP) - 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 and set a new round of negotiations for next month. European Union foreign policy chief Catherine Ashton said the meeting between Iran's top diplomat and foreign ministers of the five permanent members of the U.N. Security Council and Germany were "substantial." She said they had agreed to "go forward with an ambitious timeframe" and that senior negotiators would meet in Geneva on Oct 15-16. British Foreign Secretary William Hague said there had been a "big improvement in the tone and spirit" from Iranian Foreign Minister Mohammad Javad Zarif 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 as Secretary of State John Kerry came face-to-face with Zarif and sat next to him at a U-shaped table. Neither Kerry nor Zarif had any immediate comment on the meeting. Iranian President Hassan Rouhani and Zarif, both in New York this week to attend the U.N. General Assembly, have said they are anxious to clinch an agreement quickly that could bring their country relief from punishing international sanctions. But the U.S. insists Rouhani must back up his calls for moderation with actions that verify Iran is not seeking to develop a nuclear weapon. 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 Barack 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. They have imposed sanctions over Iran's refusal to halt enrichment. Uranium enriched to low levels can be used as fuel for nuclear energy but at higher levels, it can be used to make a nuclear weapon. Rouhani also insisted that any deal be contingent on all other nations declaring their nuclear programs, too, are solely for peaceful purposes - alluding to the U.S. and Israel. Those conditions underscored that there is still a large chasm to be bridged in negotiations. Rouhani has made a series of appearances and speeches since arriving in New York and has held bilateral negotiations with France, Turkey and Japan among others. He has come across as a more moderate face of the hard-line clerical regime in Tehran and appears to be trying to tone down Ahmadinejad's caustic rhetoric against Israel - a point of friction in relations with the U.S. On Thursday, he called for worldwide disarmament of nuclear weapons as "our highest priority." "No nation should possess nuclear weapons, since there are no right hands for these wrong weapons," he told the first-ever meeting of a U.N. forum on nuclear disarmament. He was speaking on behalf of the Non-Aligned Movement, an organization of mostly developing countries. He repeated the organization's long-standing demand that Israel join the international treaty banning the spread of nuclear weapons. Israel, which has repeatedly accused Iran of aspiring to build a nuclear bomb is the only Mideast state that has not signed the landmark 1979 Non-Proliferation Treaty. Israel reacted angrily to the remarks. "Iran's new president is playing an old and familiar game by trying to deflect attention from Iran's nuclear weapons program," said Intelligence and International Affairs Minister Yuval Steinitz. "The problem of the NPT in the Middle East is not with those countries which have not signed the NPT, but countries like Iran, Iraq, Libya and Syria which have signed the treaty and brazenly violated it," he added. "Unlike Iran, Israel has never threatened the destruction of another country," he said. Rouhani also met Japanese Prime Minister Shinzo Abe, who urged "concrete progress" on settling the nuclear issue. Abe also said the window of opportunity "will not be open forever," according to Japanese Foreign Ministry assistant press secretary Masaru Sato. Rouhani responded that he aimed to settle the nuclear issue at "an early juncture," Sato said. It was the first meeting between leaders of Japan and Iran since 2008. Rouhani was elected after a campaign that pledged to seek relief from the international sanctions. He has welcomed a new start in nuclear negotiations in hopes they could ease the economic pressure. He has said he has the full support of Iranian Supreme Leader Ayatollah Ali Khamenei, who has the final word on all important matters of state, including the nuclear question. Zarif, who Rouhani has designated his lead nuclear negotiator, has urged step-by-step compromises to advance the negotiations. That may explain why Zarif has call to reach a deal in shortest timeframe possible. Already, Iran's powerful Revolutionary Guard force has grown increasingly uneasy over Rouhani's outreach to the West as well as his apparent backing from Khamenei, who has told the Guard to steer clear of politics. The Guard has warned Rouhani about moving too fast on his overtures.