Obama administration officials at a Senate hearing Tuesday refrained from backing proposed Iran sanctions legislation or giving a deadline for Teheran to halt uranium enrichment during its negotiations with the US and other world powers. Yet US Deputy Secretary of State James Steinberg said that "we would be prepared to move ahead swiftly and effectively with additional [sanctions] measures" if the talks, which he stressed were not open-ended, failed to bear fruit. He expressed skepticism over Iran's intentions, saying the administration was "realistic" about the prospects of engagement; he later said that Iran's initial gestures are "the first concrete evidence we've had during this administration of serious negotiations." When pressed by Democrat Sen. Robert Menendez of New Jersey, though, on how long Iran has to halt its uranium enrichment - a demand of the international community which Iran has yet to adhere to - Steinberg said instead that stopping uranium enrichment is "the requirement of the UN Security Council and it's the priority in our negotiations." Menendez responded, "You don't want Congress to pursue the legislations, but at the same time you don't give us a time frame - that makes many of us uneasy." When asked pointedly by other lawmakers whether the administration supported the sanctions legislation that Congress is considering, Steinberg did not give a clear response. And when asked his thoughts on a central tenet of the legislation - blocking refined petroleum imports to Iran - he said, "We still have not reached a firm judgment on whether that would be the best way to go, in part because we need a better understanding of what the efficacy would be; in part because it would depend on the degree to which others participated in this." Both Steinberg and his co-witness, Stuart Levey, Treasury under secretary for terrorism and financial intelligence, stressed the importance of multilateral sanctions and implied that unilateral US moves, such as those before Congress, could hurt efforts to bring more countries on board. In fact, they assessed that more countries are now willing to consider stricter sanctions because of the outreach that the US has until now conducted, citing this as an achievement even if Iran was not moved by such diplomacy. "There is a strong sense that these efforts will pay off," Steinberg said of conversations with other world powers. "And frankly, the spotlight now is on Iran. We've come to the table. Everyone's looking for their response." Yet several members of Congress expressed impatience with the administration as well as Iran and evinced a desire to move ahead with sanctions, with even senators from Obama's Democratic party on edge. Democratic Sen. Chuck Schumer of New York said, "I find it troubling that the administration is not... supportive of the strongest sanctions possible." Connecticut Democratic Sen. Chris Dodd, who chaired Tuesday's hearing, recently announced that he would be including several pieces of legislation already in play, on blocking refined petroleum imports to Iran and making divestment from Iran easier, in a new bill with expanded provisions, including expanded restrictions on financial transactions and trade involving Iran. The measures would also need to be adopted by the House of Representatives, which has been looking at more narrow provisions. Still, one Capitol Hill staffer who works on the issue of Iran said that the administration and Congress are on the same schedule when it comes to legislation because they are both looking toward the deadline set out by US President Barack Obama on reevaluating the progress on negotiations by year's end. "At the moment, we're very much in sync, which is that if there isn't tangible action by the end of year, there will be consequences, and that's what I think Congress is on track to do," he said. Several senators also raised questions about America's willingness to give Iran an additional week to allow International Atomic Energy Agency inspectors into the newly revealed reactor outside Qom. "We want the IAEA to do the kind of work it needs to do to make sure that these inspections are effective... It's not just the question of walking into the site but actually doing the preparatory work," Steinberg said. "It's our judgment that this is within the period of time [and] that we will still get a good insight into what's going on." He described the other major concession Iran initially agreed to in the Geneva talks last Thursday - in which Iran would transfer large amounts of its enriched uranium stockpile abroad for processing into nuclear fuel - as important in giving the international community more breathing room to deal with the nuclear issue. Since then, however, Iran appears to have started backing away from the commitment, which Steinberg affirmed it had made. The point was echoed by US Secretary of State Hillary Clinton, who also said Monday night that last week's historic joint talks with Iran were a limited success, in a conversation conducted alongside Secretary of Defense Robert Gates to be broadcast on CNN. She was quoted as saying that "on balance, what came out of the meeting in Geneva was positive." Asked if the Iranians were committed to resolving the dispute over their nuclear program, Clinton said, "We don't know yet. We don't know." Gates said that he has always been convinced that Iran intends to develop nuclear weapons. But he there is a possibility that Iran can be persuaded that the weapons would be counterproductive in the long run, he said. Their comments came as a new Pew poll found that Americans strongly support war against Iran if sanctions fail. Some 61 percent back military action to prevent Iran from acquiring nuclear weapons, with only 24% calling for the US to avoid military action at the cost of allowing Iran to get nukes. Just a few percentage points higher, 63% back direct negotiations, while 78% favor sanctions, but only 22% and 32%, respectively, thought the two tactics would work. Overall, 51% of Americans say they have confidence in Obama to "do the right thing" on Iran. The telephone survey was conducted over the past week among 1,500 Americans. Meanwhile, Iran has reportedly complained to the UN and American negotiators about Iranian citizens it believes the US is holding. Ali Reza Asghari, an Iranian deputy defense minister and a prominent leader of the Revolutionary Guards who disappeared two years ago in Turkey, and Shahram Amiri, a nuclear physicist who Iran's Foreign Ministry has said disappeared during a visit to Saudi Arabia in late May or early June, are believed to have defected from Iran and some have speculated that at least one has been crucial to supplying America information about Qom. AP contributed to this report.