The United States has stepped back from the notion of "regime change" in Iran, US Sen. John Kerry stressed Wednesday, urging that Iran also moderate its actions. "We are not in a regime change mode," said the chairman of the Senate Foreign Relations Committee during a hearing on the Islamic Republic. "Just as we abandon calls for regime change in Teheran and recognize a legitimate Iranian role in the region, Iran's leaders must moderate their behavior and that of their proxies, Hizbullah and Hamas." Kerry praised the Obama administration's focus on diplomacy with Iran, adding that "engagement alone is not a strategy and talks are not an end in themselves." The Senate committee is set to release a report on Iran and its nuclear ambitions Thursday. Kerry also raised questions about the utility of sanctions, an option the administration has threatened to ramp up if talks fail. "Sanctions - even coordinated, multilateral sanctions - are a blunt instrument with an imperfect track record. When it comes to Iran, the verdict on them is mixed at best," he said. "Sanctions slowed Iran's nuclear program, but they did not prevent it from acquiring the capacity to enrich uranium on an industrial scale." Still, he described sanctions as "far more likely" to succeed that military force when that possibility was raised by witness Nicholas Burns, a top State Department official in the Bush administration tasked with the Iran portfolio. "I don't see Iran negotiating seriously if there isn't a marriage between diplomacy and the threat of force. It's a language they understand," said Burns, who recommended that the Obama administration to reiterate the possibility that force could be used. In response to Burns's comments, State Department Spokesman Robert Wood said later Wednesday that, "Our policy's very clear. We're pursuing diplomacy, a two-track approach with our other partners â€¦ and that's where our efforts are focused." Burns emphasized that he didn't think force should be seriously considered in the near term, and also cautioned that "I don't think it could work" if used later on. For now, he praised the Obama approach to the issue and its focus on engagement, differing from recent comments from Foreign Minister Avigdor Lieberman that only three months should be allowed for diplomacy. "My assumption is there is time," he said, though added that a timetable should be set so negotiations don't continue indefinitely. On Tuesday, Kerry defended the Obama administration's approach on Iran in a speech before the American Israel Public Affairs Committee. "When we have engaged effectively with hostile nations in the past, we did so fortified by moral authority, committed allies, and the strongest military in the world," he said. "That's exactly how we should engage Iran today - not to accept the unacceptable, but to make sure Iran never gets a nuclear bomb."