In addition, diplomats said Iran will open its newly disclosed nuclear plant to UN inspectors, probably within a few weeks.
Adding to the optimism generated by the decision to hold follow-up talks was a rare bilateral meeting between the senior US and Iranian delegates to the meeting.
US Deputy State Department spokesman Robert Wood said Undersecretary of State William Burns used the meeting with chief Iranian delegate Saeed Jalili "to reiterate the international community's concerns about Iran's nuclear program.
"He addressed the need for Iran to take concrete and practical steps that are consistent with its international obligations and that will build international confidence in the exclusively peaceful nature of its program.
"While the focus of the discussion was on Iran's nuclear program, both sides had a frank exchange on other issues, including human rights," said Wood.
The encounter appeared to be concrete proof of President Barack Obama's commitment to engage Iran directly on nuclear and other issues — a sharp break from the policy under the Bush administration.
More broadly, the meeting suggested that Obama was putting his concept of US foreign policy into action, with its emphasis on negotiating even with the nations that are most hostile to the United States.
New site up for inspectionConfirming that the seven nations planned to meet again, senior EU envoy Javier Solana said Iran had pledged to open its newly revealed uranium enrichment plant to International Atomic Energy Agency inspection soon.
Iran's disclosure of the new plant had threatened to poison the atmosphere of the talks, with the West saying Tehran only revealed it because it feared it would found out. Uranium enrichment can make both nuclear fuel and the fissile core of nuclear warheads.
Solana said Iran had pledged to "cooperate fully and immediately with the IAEA" and said he expected Tehran to invite agency inspectors looking for signs of covert nuclear weapons activity to visit "in the next couple of weeks."
At the United Nations, the Iranian Foreign Minister suggested his country's talks with the US and five other world powers could be expanded to the "summit" level.
Manouchehr Mottaki said Iran was willing to discuss a variety of security, economic and political issues, although he did not specifically refer to nuclear issues, which the six powers consider the most critical topic.
The five permanent members of the UN Security Council — the US, Russia, China, Britain and France — plus Germany hope to persuade Tehran to freeze the enrichment program.
Going into Thursday's talks, one of the top US goals was to get the Iranians to commit to a second round of talks within a couple of weeks in order to keep the dialogue in a compact timeframe. The US assumption was that if Iran was willing to engage seriously on the nuclear issue, a positive sign would be its agreement to have a second meeting shortly.