Rouhani, considered the most moderate candidate on a ballot full of conservatives, will take over for former President Mahmoud Ahmadinejad, who was not allowed to run for another term after leading Iran for the last eight years.
By winning 50.8 percent of the vote, Rouhani avoided a second-round run-off election. He gained much attention after indicating during his campaign that he would pursue a less-confrontational foreign policy and would enact a "civil rights charter" in Iran.
In Washington, a White House spokesman said President Obama hopes "the Iranian government will heed the will of the Iranian people and make responsible choices that create a better future for all Iranians."
The administration expressed some measure of optimism that with this change in leadership, a diplomatic solution to ending Iran's rogue nuclear program can be reached.
But while a more moderate president would make Iran potentially easier to deal with, Israeli Prime Minister Benjamin Netanyahu cautioned his allies that Supreme Leader Ayatollah Ali Khamenei remains the real source of power in the theocratic government.
Netanyahu, who has hinted at preemptive strikes against Iran to stop the development of nuclear weapons, said on Sunday that the international community must not remove crippling economic and political sanctions against Tehran.
If anything, the Israeli leader said that sanctions should be stepped up now because "the more pressure increases on Iran so will the chance of ending Iran's nuclear program which remains the biggest threat to world peace."
Yuval Steinitz, Israel's minister of intelligence and strategic affairs, agrees with Netanyahu, saying, "As long as we don't see a change it's better to be wary and not celebrate prematurely."
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