US President Barack Obama characterized Thursday's landmark meeting with Iran as a "constructive beginning," following Iran's apparent agreement to open its nuclear facilities to inspection, to meet again later in the month and in principle to have a third party provide it with nuclear energy. "Today's meeting was a constructive beginning, but it must be followed by constructive action by the Iranian government," Obama said during a brief White House appearance following the talks held in Geneva. He gave Iran two weeks to allow IAEA inspectors into its recently revealed second uranium enrichment facility at Qom. "Iran must take concrete steps to build confidence that its nuclear program will serve peaceful purposes - steps that meet Iran's obligations under multiple UN Security Council resolutions," said Obama of resolutions that demand Teheran stop enriching uranium. He called Iran's willingness to import such material for its research reactor "consistent with that objective - provided that it transfers Iran's low-enriched uranium to a third country for fuel fabrication." Obama also stressed that "we're not interested in talking for the sake of talking," and warned that "if Iran does not take steps in the near future to live up to its obligations, then the United States will not continue to negotiate indefinitely, and we are prepared to move toward increased pressure." Iran will have two weeks, Obama said, to follow through on the commitments Western officials announced following the seven-way Geneva meetings, the first in which the United States held substantive direct discussions on the Iranian nuclear program with Teheran. Israel, though, had no expectation that Thursday's talks, which EU foreign policy chief Javier Solana said would continue with at least another session before the end of the month, would culminate in any dramatic development. Rather, one government official said, this is another round in a more than decade-old process to stop Iran's nuclear development. While Israel is skeptical overall with regard to the talks, assessments in the IDF are that Iran, while radical, is still a practical country that would be open to the possibility of reaching a deal with the West. The government official said the revelation last Friday of the clandestine uranium enrichment facility being constructed in a mountain near Qom, a facility Solana said the Iranians agreed Thursday to open up to IAEA inspection, had given the Western powers - at least temporarily - the upper hand in that they could say they had caught the Iranians cheating red-handed. US State Department Under Secretary of Political Affairs William Burns held a bilateral conversation with chief Iranian delegate Saeed Jalili during the lunch break of the day-long meetings held under the auspices of the P5+1 group, which includes the US, Russia, China, Britain, France and Germany. State Department officials said that during that conversation, Burns had reiterated America's concerns about Iran's nuclear program, as well as raised the issue of human rights in Iran and American citizens being held by Teheran. Though Iranian officials had originally said they would not even address the nuclear issue, that subject formed the heart of the talks, according to participants. In his remarks following the Geneva meetings Thursday, Obama said UN International Atomic Energy Agency head Mohamed ElBaradei would be traveling to Iran in a few days and had "my full support, and the Iranian government must grant the IAEA full access to the site in Qom." The Associated Press quoted the IAEA as announcing that ElBaradei was "invited to Teheran by Iranian authorities." ElBaradei recently described Teheran as "on the wrong side of the law" regarding the second enrichment site near Qom, saying that Iran should have revealed its plans as soon as the decision was made to build the plant. Western intelligence agencies, meanwhile, suspect that Iran likely has additional secret nuclear installations scattered throughout the country. The assessment in some Western countries is that Iran likely has additional facilities that are either connected to the enrichment center discovered near Qom or are independent. But not everyone is convinced about Friday's revelation of the facility near Qom. Visiting Russian Deputy Prime Minister Victor Zubkov, when asked whether the revelations of the facility would alter Russia's so-far reticent position on sanctions, told The Jerusalem Post, "There has been no proof yet or confirmation, and we need to verify and know what has been done, and since there has not been enough proof and evidence, we have to work on that. I think the rumors might be exaggerated. However, a strong monitoring mechanism should be in place." Still, Zubkov stressed that "we in Russia cannot accept in any way that Iran could possess nuclear weapons. That is totally unacceptable to us." White House spokesman Robert Gibbs declined to answer questions on whether the US believed Iran had additional undisclosed nuclear sites. But earlier Thursday, Sen. Joseph Lieberman indicated that he thought the Islamic Republic could well have further facilities. "In the wake of last week's disclosure, there is renewed urgency and imperative surrounding the question of what else the Iranians have been hiding. Given that the international community has now twice uncovered secret enrichment facilities in Iran, it is reasonable to suspect there are likely others as well," he said at an American Enterprise Institute event. "Their past actions put the burden of proof on Iran," he said. "The only way for the Iranians to prove otherwise is for them to provide the IAEA with full, unrestricted access to every site, every scientist, every scrap of paper, and every piece of equipment that they want to see." He stressed that "it is not enough for the Iranians to engage in a process in Geneva today. That process needs to yield results, and quickly. My own belief is that the current Iranian leadership will only consider stepping back from the nuclear brink when they are convinced that if they fail to do so, there will be consequences so severe that the continuity of their regime will be threatened." Lieberman said the US - unilaterally if necessary - needed to look at further sanctions, such as blocking refined petroleum imports to Iran, as a bill he had co-sponsored would do. Speaking after Thursday's meetings, US Secretary of State Hillary Clinton sounded a note of caution. "I will count it as a positive sign when it moves from gestures and engagement to actions and results," she said. "We want to see concrete actions and positive results. And I think today's meeting opened the door, but let's see what happens." But at least one Iran expert, Jim Walsh of the Massachusetts Institute of Technology's Security Studies Program, assessed that the extent to which Teheran had agreed to take concrete steps was a significant - and unexpected - move. "I'm surprised at the outcome," said Walsh, speaking on Fox News. He pointed particularly to its willingness to have a third party take care of enrichment. "That is a very important principle. That's saying we'll let an outside party handle part of the enrichment process," he explained. "This is a big deal to have happened at the first meeting." Yet Ilan Berman of the American Foreign Policy Council was more skeptical about the nature of Iran's commitment. "This doesn't eliminate the real concern," he said on MSNBC, describing the true threat as Iran's ability to enrich uranium and otherwise produce nuclear weapons, potentially in secret, regardless of external processing. "That concern's still on the table." Israel, continuing a policy in place for a week, refrained from commenting officially on the talks in Geneva, saying that there was no need for Israel to take a high profile at this time. Jerusalem, one official explained, was behind the scenes trying to ensure both that the world recognized the severity of the situation, and kept to its own demands. Prime Minister Binyamin Netanyahu, at Thursday's cabinet meeting, singled out Canadian Prime Minister Stephen Harper for showing "leadership and moral clarity" on the Iranian issue. Netanyahu also praised French President Nicolas Sarkozy for taking a very assertive position on the matter, and said that the combination of the violent Iranian crackdown following June's presidential election there, and the recent discovery of the facility near Qom, had led to a firmer position from other European countries, as well as from the Americans. He said that while from a diplomatic point of view, the situation vis-Ã -vis Iran was improving, on the ground there had been no change in Iranian behavior, and their uranium enrichment continued unabated.