The Obama administration has cautiously welcomed the Iranian gestures coming out of the talks over its nuclear program last week, saying they are a "constructive beginning" even if much more work is needed and progress cannot be taken for granted. But many Washington hands are warning that the key factor behind the more cooperative approach Iran is taking has been a shift in America's posture rather than in Teheran's. The Islamic republic last week indicated it would allow inspectors into the recently revealed Qom reactor, and agreed in principle to the transfer of much of its enrichment uranium abroad for conversion into nuclear fuel, meeting the initial demands of the world powers negotiating with Iran. But halting uranium enrichment, a key demand of the international community, was not affected by the discussions on Thursday and the Iranians are now calling into question just what was agreed to on fuel processing abroad at the meeting. "Obviously they're talking more softly and more nicely," Iran expert Ilan Berman said of the Iranians. He attributed that attitude to their having "picked up that negotiations, diplomacy, engagement is the language the Obama administration is trying to speak." While the Bush administration focused on threatening pressure that it didn't follow through on - and which Iran ignored by "digging in its heels" - Berman said the Iranians assess now that talking will buy time, that "engagement with the United States will make it less likely that the US will sanction or bomb them. That's what's informing this new Iranian willingness to enter negotiations." Anthony Cordesman of the Center for Strategic and International Studies, author of a new book on Iran, also underscored that the more conciliatory stance Iran has adopted following last Thursday's meeting with the US and five other world powers is consistent with a long history of weaving between cooperation and resistance, all while continuing to press ahead with its nuclear program. "Historically it doesn't mean much," he said of Thursday's outcome. "The combination of growing European anger over the lack of responsiveness and the outing of the facility at Qom plus the scandal over the election has made them much more cooperative," he continued. "We don't know what the Iranian offers really mean. There's no formal agreement as of yet." The domestic weakening of the regime did contribute to a "big shift" in the stance of Iran toward the US, contended one Iranian-born Washington-based scholar, who asked that his name not be used. "They are very much paranoid about the West, but they might not think isolation at this point will help them," he said. "Now, because the government has lost the domestic support it used to enjoy, it wants to resolve international issues so it can deal with the domestic issues." But he gave even more weight to changes in the US perspective. "Obama agreed to remove preconditions to talking to Iran," he noted, referring to the Bush administration demand that Teheran stop enriching uranium before sitting down with the US. And, he said, "There's even some recognition of Iran's right to enrich uranium," as part of the Non-Proliferation Treaty regime. Michael Rubin of the American Enterprise Institute was even more emphatic: "What we've done is we've shifted our position. They haven't shifted theirs." The willingness of the US to tolerate some nuclear capabilities under the NPT that the Iranian scholar pointed to has also led to talk from observers on both sides of the aisle that America could be headed toward a situation of containment of Iran rather than prevention of nuclear capacity. A State Department official brushed off the suggestion on Monday, saying, "We are in an intensive diplomatic phase now. The discussions we had with Iran on October 1 were a constructive beginning, but must be followed by constructive action. It will not be open-ended." At other times, administration officials - and US President Barack Obama himself - have insisted that a nuclear-armed Iran is unacceptable and that a program of diplomacy and sanctions that does not rule out military force will be used to keep Teheran from acquiring a nuclear bomb. But voices outside the administration, including that of Washington Post columnist Jackson Diehl in his Sunday op-ed, are assessing that "none of the steps the West is considering to stop the Iranian nuclear program is likely to work," and pointing to containment as the likely fallback position. He described that as a scenario limiting "Iran's ability to produce nuclear weapons or exercise its influence through the region by every means possible short of war - and to be prepared to sustain the effort over years, maybe decades." Diehl quotes Brookings Institution expert Kenneth Pollack as offering this assessment: "In their heart of hearts I think the Obama administration knows that this is where this is going," Pollack, a former Clinton official, said. Berman said the Obama administration's approval of the NPT provisions for Iran could enable Teheran to legally acquire much of what it would need for a nuclear weapon, complicating any scenario other than containment. He also noted that even the recent agreement in principle Iran has been said to have made as a first step in the current negotiations - shipping much of its current enriched uranium stockpile abroad for conversion into nuclear fuel - wouldn't stop Iran from taking the material it receives and enriching it further or otherwise carrying on secret enrichment activity. Cordesman put the issues in more immediate terms. Given the state of Iran's technological know-how, spinning centrifuges and concealment abilities, at this point, "the problem we have is that Iran has reached a point where virtually everything you do is containment," he said.