GENEVA, Switzerland (CNN) -- Iran says it plans to cooperate "fully" with the U.N. nuclear agency and will invite representatives of the body to visit its newly revealed uranium enrichment facility "soon," said Javier Solana, the European Union foreign policy chief.
Solana also confirmed that world powers and Iran will hold another round of talks before the end of the month. He spoke at a news conference Thursday after the Geneva talks.
The meeting occurred on the heels of the recent revelation that Iran was building a second uranium enrichment facility near the city of Qom, a dramatic development that jacked up tension between Iran and international powers.
Iran participated in the talks along with the EU, Germany and the five permanent members of the U.N. Security Council: the United States, Britain, France, Russia and China.
Two top officials from the United States and Iran huddled on the margins of the Geneva talks, a meeting one diplomat describes as "serious and frank."
William J. Burns, U.S. undersecretary of state for political affairs, is leading the U.S. delegation, and Saeed Jalili, Iran's nuclear negotiator, is representing his country at the meeting, a senior U.S. official and a diplomatic source confirmed.
The men discussed the nuclear program, a sit-down described as the first face-to-face meeting over the Iran's nuclear program.
Another diplomatic source, who characterized the meeting as "serious and frank," said world powers are pushing for a date for International Atomic Energy Agency inspectors to examine the recently revealed nuclear facility in Qom.
They also discussed human rights issues, including detained Americans in Iran. Among those held in Iranian custody are three hikers who strayed from Iraqi territory into Iran.
The sources would talk only on the condition of anonymity because of the sensitive nature of the ongoing discussions with Iran.
"They certainly are historical talks," said David Albright, president of the Institute for Science and International Security and a former weapons inspector. "For the United States and Iran to sit down finally and start to talk about the significant differences between the two countries is extremely important, and I think it's long overdue."
The group met at the Villa le Saugy.
The mood at the event's buffet-style lunch seemed to belie the stark international tensions over the Iranian nuclear issue. Iranians and the other officials dined and mingled, and some ate while seated, and others stood at tables, an official at the talks said.
Many gathered in the villa's backyard and enjoyed a view of Lake Geneva and the Swiss Alps, the official said. Along with the U.S. and Iranian officials, many other would huddle together, quietly discussing issues in sidebar conversations, the official said.
The existence of the second uranium enrichment facility prompted President Obama and the leaders of Britain and France to publicly chide the Islamic republic last week at the G-20 summit in Pittsburgh and threaten further sanctions.
Iran claims that its nuclear program is intended for peaceful purposes, but many in the international community have accused the country of trying to develop a nuclear weapons capability.
One official said international powers wanted to know what kind of "steps" Iran is "willing to take to build confidence with the international community."
According to three senior U.S. administration officials, the United States wants IAEA nuclear monitors to have unfettered access to the facility.
The first option would be to persuade Iran to change its ways through dialogue, but if that fails, then isolation and sanctions are other options, they said.
"If it's not going to succeed, then there has to be consequences," an official said.
Pressure could also come from the U.N. Security Council, the United States or other like-minded nations.
"They will respond," one official said of Iran. "If not, they will pay the price."
But former U.S. President Carter urged Washington and other nations to take a diplomatic approach in negotiations with Iran over the country's nuclear ambitions.
"I hope and pray that Iran will be induced to permit international inspectors to come in and observe their entire nuclear program, because what they're doing so far is completely illegal under the nonproliferation treaty," Carter said Thursday.
"They have a right to purify uranium and plutonium to use for nuclear power. If Iran is on the borderline, the constant threats that we or the Israelis are going to attack Iran is the best thing to force them to say, 'Let's defend ourselves.'
"I don't think Iran has made up their mind what to do, and I think the best thing we can do is engage them and stop making these idle threats."