Reuters From Los Angeles to Paris to Tehran, disparate opposition groups with little in common but an aversion to Iran's clerical leaders are struggling to extract political gains from an escalation in Western sanctions. Numerous dissidents have hailed Western agreement on tougher measures to compel Iran to rein in its nuclear program, but translating the upbeat mood into renewed opposition activity will not be easy, Iran experts say. Internally, opposition forces are at a low ebb following the bloody suppression of a loose reformist street protest movement they mounted in 2009. Iran's factionalized clerical authorities may be riven by their own disputes, but the security apparatus has a tight grip on domestic dissent and its leaders are under house arrest. Overseas, the complexity of the dissidents' task has roots in the opposition's very diversity: The communities of monarchists, communists and liberals and others can agree on little beyond ending the three-decade rule of clerics. Discord extends to the utility of sanctions as an instrument of leverage: Exiled groups tend to favor them. But dissidents at home are less enthusiastic, arguing that the measures will hit the middle class from which the 2009 protests sprang. One thought found among oppositionists on both sides of the internal-external divide is the fear that the curbs could raise regional tensions and trigger a devastating conflict. “If you corner a cat, you should expect it to show its claws,” said a leading reformist politician, who asked not to be named due to the sensitivity of the matter. “If the authorities feel that they have no alternative, they might do anything, including interrupting shipments of oil.” On New Year's Eve, US President Barack Obama signed into law the toughest financial sanctions yet against Iran, which if fully implemented could make it impossible for most countries to pay for Iranian oil. The European Union, which still buys a fifth of Iran's 2.6 million barrels per day of exports, is expected to announce an embargo this month. For the sanctions now to be effective, the governments of the United States and Europe must “make it known to the Iranians that they understand the lot of Iranians, and they understand the harsh situation they are living in,” Ganji said. “It all depends on how they are going to present it to the Iranian people,” he added. The French-based National Council of Resistance of Iran (NCRI), which has followers across Europe and the United States, supports the tougher sanctions but argues that only “regime change” will prove to be an effective policy. The NCRI was responsible for arguably the most influential opposition move in years when it became the first group to expose Iran's covert nuclear program in 2002. It says it has huge backing within Iran although analysts say its support is very hard to gauge. Its leader Maryam Rajavi told Reuters the tougher sanctions “should have been undertaken a long time ago.” She suggested the Iranian authorities were bluffing about closing the Hormuz Strait and only engaged in this tactic “because they are confident of the West's indecisiveness”. Others, such as US-based Ali Shakeri, 63, are sceptical about the usefulness of economic curbs. The Iranian-born peace campaigner and businessman says sanctions especially hurt the average citizen. He said: “Any society without a middle class, with the oppressed people and the elite of billionaires, is not going to end up to any democracy.” __