Senate Bill Threatens Nuclear Deal, Analysts Say Proponents of Senate legislation that threatens Iran with tough new sanctions if nuclear negotiators fail to reach a comprehensive agreement contend it will pressure the Iranians to honor the pledges they made in an interim deal reached in Geneva a month ago. But a number of American and Iranian political analysts say the legislation could have the opposite effect by undermining President Hassan Rouhani, whose outreach to the Americans already appears to have weakened his political maneuverability at home. The Obama administration's condemnation of the legislation, introduced Thursday, was partly aimed at assuring Mr. Rouhani that it has little prospect of advancing. President Obama said he would veto the bipartisan bill, the Nuclear Weapon Free Iran Act of 2013, if it ever reached his desk. Even so, there are already indications that the conservative hard-liners in Iran's hierarchy, whose influence over nuclear policy was temporarily diminished with the election of Mr. Rouhani six months ago, see the introduction of such legislation as a vindication of their deep suspicions about American motives. Experts on Iranian politics said the hard-liners may use that legislation to reassert themselves. While American proponents of the legislation contend it makes the cost to Iran of quitting the negotiations too high, Iranian political experts say that view does not reflect how the legislation is viewed in Iran. "The move to sanction now will prove the hard-line narrative that the premise is wrong and will strengthen the standing of that argument and its proponents," Farideh Farhi, an Iranian scholar at the University of Hawaii, said in an email. But even more important is the fact that further sanctions at this time will kill the process initiated in Geneva. The Rouhani government will have no choice but to abandon it. Mr. Rouhani won the election in June in part by promising to solve Iran's economic malaise, end its isolation and ease the strict social and political restraints that have shaped life in the country for many years. He has made a priority of resolving the nuclear dispute, aiming to free the country from the crippling economic sanctions imposed by the United States and European Union over their suspicions that Iran aspires to develop nuclear weapons, which the Iranians deny. But Mr. Rouhani has failed, so far, to make good on his pledges of social and political change. His supporters in Iran are still waiting for him to free basic restrictions on Internet use, allow more press criticism and release political prisoners. What has become increasingly clear, according to some Iran analysts, is that Mr. Rouhani has limited authority in those realms, or at least needs a nuclear agreement first to show that a negotiated settlement is possible, which could mute the criticism of his own more conservative rivals. While Mr. Rouhani still appears to have the support of Iran's supreme leader, Ayatollah Ali Khamenei, it is evident from Ayatollah Khamenei's own statements that he is profoundly suspicious of the nuclear negotiations and any outreach to the West - the United States in particular. Hard-liners in Iran felt empowered last week when Ayatollah Khamenei gave a lengthy speech about the invasion of Western influences and Iranian culture, which he compared to a garden. "You should not allow weeds to grow," he said. Those remarks were widely viewed as a hint that Ayatollah Khamenei, for now, wants to remain in tight control of the Internet, media and other fields of culture. Alireza Nader, an Iran specialist at the Washington offices of the RAND Corporation, a research organization, said that based on Mr. Rouhani's apparent unwillingness or inability to keep his domestic promises, "the nuclear issue is his specific portfolio." Cliff Kupchan, an Iran specialist at the Eurasia Group, a political-risk consulting firm in Washington, said impatience for change among Mr. Rouhani's own followers is also creating problems for him. "Rouhani needs success on the nuclear issue to consolidate power and move to liberalize domestic issues," Mr. Kupchan said. Put another way, he said, "Rouhani has the authority to get sanctions relief. Either he brings home the bacon soon, or he loses his clout. Thomas Erdbrink contributed reporting from Tehran.