The head of the UN nuclear watchdog set October 25 as the date for his inspectors to check Iran's newly revealed uranium enrichment site and struck an upbeat note Sunday, saying Teheran's confrontation with the West is shifting gears to more cooperation and transparency. Though the United Nations has no "concrete proof" of an ongoing nuclear weapons program, the chief of the UN's International Atomic Energy Agency, Mohamed ElBaradei, said he has "concerns about Iran's future intentions." The inspection of the site and the outcome of more nuclear talks later this month with the US and its allies will be crucial in determining the direction of the six-year standoff over Iran's nuclear activities. "I see that we are at a critical moment. I see that we are shifting gears from confrontation into transparency and cooperation," ElBaradei said at a news conference in Teheran with Iran's top nuclear official, Ali Akbar Salehi. His visit followed a week of intense diplomatic activity surrounding Iran's nuclear program, set off by the revelation that Teheran had been secretly constructing a new uranium enrichment plant just north of the holy city of Qom. On Thursday, Iran and six world powers put nuclear talks back on track at a landmark session near Geneva that included the highest-level bilateral contact with the US in years. President Barack Obama's national security adviser said Sunday that Washington was also pleased with the level of cooperation from Iran. "The fact that Iran came to the table and seemingly showed some degree of cooperation, I think, is a good thing," James Jones said on CNN's "State of the Union" program. "But this is not going to be an open-ended process. ... We, the world community, want to be satisfied within a short period of time," Jones added. "So it's not going to be extended discussions that we're going to have before we draw our conclusions to what their real intent is. But for now, I think things are moving in the right direction." French Foreign Minister Bernard Kouchner also talked of a "wind of medium optimism." He said "something happened" at Thursday's talks in Switzerland and "we no longer want to talk of sanctions." ElBaradei was in Iran to set up the UN inspection of the enrichment facility near Qom. The site sparked serious concern, in part because its location next to a military base and partly inside a mountain adds to suspicions that Iran's nuclear program could have a military dimension. Obama, who accuses Iran of seeking to keep the site hidden for years before notifying the IAEA about it, has said Teheran's actions "raised grave doubts" about its promise to use nuclear technology for peaceful purposes only. Iran, which insists its nuclear work is only for nonmilitary purposes like energy production and medical research, says the site's location near a military base is intended to protect it from potential aerial bombing. "It is important for us to send our inspectors to do a comprehensive verification of that facility, to assure ourselves that it is a facility that is built for peaceful purposes," ElBaradei said, seated beside Salehi, the head of Iran's nuclear agency. "We agreed that our inspectors would come here on the 25th of October to do the inspection and to go to Qom and I hope and I trust that Iran will be as transparent with our inspectors team as possible." The US ambassador to the UN stated that the permanent members of the UN Security Council are studying options for more sanctions if Iran does not fully open its nuclear program to international inspections. "But right now we are in a period of intense negotiations," said Ambassador Susan Rice, speaking on NBC TV's "Meet the Press." "It's not an infinite period. It's a very finite period," she said, while refusing to set a deadline. Iranian President Mahmoud Ahmadinejad told ElBaradei that Iran's cooperation with the agency has left no ambiguity over Teheran's nuclear activities. "Outstanding issues were resolved due to good cooperation between Iran and the agency," state TV quoted Ahmadinejad as saying. "Today, there are no ambiguous issues left." But the IAEA says there are still issues that Iran needs to clarify, including alleged studies by Iran on high explosives and a missile delivery system for a nuclear warhead. "As I have said many times and I continue to say today, the agency has no complete proof that there is an ongoing weapons program in Iran," ElBaradei said. "There are allegations that Iran has conducted weaponization studies. However these allegations we are still looking into and we are looking to Iran to help us clarify," he added. Iranian officials have challenged Obama's accusations that they sought to keep the new enrichment site hidden, saying a September 21 letter informing the IAEA about the facility was sent a year earlier than required. "We disagree with the interpretation of Iran. ... Iran should have informed the IAEA the day it decided to construct the facility," ElBaradei said. The Nuclear Non-Proliferation Treaty's Additional Protocol requires notification before construction starts. The Additional Protocol, which Iran says it stopped implementing in response to UN sanctions, also allows intrusive inspections. "It is important to us that Iran reapplies the Additional Protocol," ElBaradei said. ElBaradei also discussed a plan to allow Russia to take some of Iran's processed uranium and enrich it to higher levels to fuel a research reactor in Tehran. He said that there would be a meeting October 19 in Vienna with Iran, the US, France and Russia to discuss the details of that agreement.