A 15-minute telephone call may not seem like much but when this represents the first direct conversation between the Presidents of Iran and the United States in 34 years, the world is bound to sit up and take notice. To get a sense of the historical significance, consider this: the last time the highest political executives from the two countries conversed was in 1979, when Jimmy Carter was U.S. President and the Shah of Iran had not yet been deposed. By all accounts, last week’s chat, which was conducted through an interpreter, was cordial, with Barack Obama reportedly expressing “deep respect” for the people of Iran, and Hassan Rouhani apparently calling the U.S. a “great nation.” While such formal remarks are common in exchanges between heads of state or government, the context makes the discussion a potentially transformative event. The public suspicion and animosity which have obtained between Washington and Tehran for the past three decades have been among the major causes of political deadlock and worse in Central and West Asia, with gross allegations and insults traded to the point where successive U.S. administrations have often seemed to be about to attack Iran. While much is yet to be addressed by both parties — even who called whom appears to be unclear — the very fact that the two Presidents talked with each other must be welcomed.

Both leaders are already facing resistance in their own countries and the path that lies ahead is difficult. President Rouhani has indicated his willingness to meet legitimate western concerns about his country’s nuclear programme but he will not be able to carry his own domestic critics unless Mr. Obama can undo a part of the unilateral sanctions Washington has imposed on Iran. Early indications are not promising. Not only does the U.S. President lack the ability to push Congress, many of whose members remain implacably opposed to any dealing with the Islamic Republic, but he himself seems unconvinced of pursuing such a goal. Indeed, his belief that sanctions have pushed Tehran towards a more open approach is undercutting the very logic of détente before the process has even begun. Secondly, Iran’s greatest regional rival, Saudi Arabia, will be very concerned about the Obama-Rouhani call, as will Israeli Prime Minister Binyamin Netanyahu. Israel was informed in advance but Bibi can be counted upon to try and throw a spanner in the works. To be sure, Mr. Rouhani faces his own uncertainties too. Nevertheless, his presidency has created the best chance in decades to start diminishing the mutual bitterness that has soured relations between Iran and the U.S. Having taken a cautious step forward, the U.S. must not waste this chance.

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