Iranians celebrated into Sunday after moderate Hassan Rohani was elected president in a popular repudiation of conservative hardliners, and he pledged a new tone of respect in Tehran's international affairs after years of increasing antagonism. Rohani, a Shi'ite cleric and former chief nuclear negotiator with Western powers, received a resounding mandate for change from Iranians weary of years of economic decline under U.N. and Western sanctions and security clampdowns on dissent. His victory goes some way to repairing the legitimacy of the Islamic Republic, punctured four years ago when an election marred by fraud allegations led to mass unrest, and may give leverage for reformist voices muzzled since then to re-emerge. But the hopeful reaction abroad was tempered by skepticism that Rohani could overcome the mistrust and alienation prevailing between Tehran and much of the world, and arch-enemy Israel warned against any complacency on Iran's disputed quest for nuclear power. "The international community must not give in to wishful thinking or temptation and loosen the pressure on Iran for it to stop its nuclear program," Israeli Prime Minister Benjamin Netanyahu said. He noted that it was Iran's theocratic supreme leader, Ayatollah Ali Khamenei, and not the president who set nuclear policy. Israel, widely believed to have the Middle East's only atomic arsenal, and the West fear Iran is enriching uranium with the aim of developing nuclear arms, an accusation Tehran denies. Rohani's surprise win will not resolve anytime soon the row with the West over Iran's nuclear ambitions or lessen its support of Syria's president in the civil war there - matters of national security decided by Khamenei. But the president runs the economy and has important influence on decision-making and Iranians clearly felt change was essential after eight years of President Mahmoud Ahmadinejad, a belligerent, populist hardliner associated with mismanagement, waste and repression. "This victory is a victory of wisdom, a victory of moderation, a victory of growth and awareness and a victory of commitment over extremism and ill-temper," Rohani told state television, promising to work for all Iranians, including the hardline so-called "Principlists" whom he defeated at the poll. State TV re-broadcast his victory speech on Sunday and its website quoted him as saying: "With their celebrations last night, the Iranian people showed they are hopeful about the future and God willing, ethics and moderation will govern the country." ROHANI WARNS AGAINST EUPHORIA However, he told the state news agency IRNA, "the country's problems won't be solved overnight and this needs to happen gradually and with consultation with experts." But Rohani said there was a new chance "in the international arena" for "those who truly respect democracy and cooperation and free negotiation". The United States said it stood ready to engage with Iran to reach a "diplomatic solution" over its nuclear program, even though it - along with Israel - have refused to rule out military strikes against Iranian nuclear sites. "We respect the vote of the Iranian people and congratulate them for their participation in the political process, and their courage in making their voices heard," the White House said in a statement. "It is our hope that the Iranian government will heed the will of the Iranian people and make responsible choices that create a better future for all Iranians," the White House said. Celebrating crowds sprang up across Tehran and other major cities as his victory was confirmed.