Iran's new president will find a partner in the United States if he comes clean on the Islamic republic's controversial nuclear program, a senior White House official said Sunday.

Moderate cleric Hassan Rowhani was elected president Friday, ending eight years of a conservative grip on the office marked by tension with the West over Tehran's atomic drive.

Hizbullah fighters and members of Iran's Revolutionary Guards are training Syrian troops to spearhead an offensive against rebel-held areas in Aleppo in Syria's north, UK's Sunday Times reported.

UK's The Independent also said Sunday that Iran has decided to send a first contingent of 4,000 Revolutionary Guards to Syria to support President Bashar Assad’s forces against the rebels.

Israeli Prime Minister Benjamin Netanyahu said Sunday the world should keep up pressure on Iran to rein in its nuclear program and avoid thinking the election of a moderate president will bring change.

"The international community should not fall into wishful thinking and be tempted to ease pressure on Iran to stop its nuclear program," Netanyahu said at the start a meeting of his cabinet.

Leaders of Gulf states, which have tense relations with Iran, have swiftly welcomed moderate cleric Hassan Rowhani's election as the new president of the Islamic republic, several state news agencies said.

"We look forward to working together for the good of this region and the Emirati and Iranian peoples," the UAE President Sheikh Khalifa bin Zayed al-Nahyan wrote in a telegram to Rowhani, state news agency WAM said late Saturday.

The United States said Saturday it is prepared to engage Iran directly over its disputed nuclear program after moderate cleric Hassan Rowhani was declared the country's new president.

The White House said such engagement would be aimed at reaching a "diplomatic solution that will fully address the international community's concerns about Iran's nuclear program."

Israel reacted to the election of Iran's new president on Saturday by saying it was supreme leader Ayatollah Ali Khamenei who decides on nuclear policy, not the president.

"Iran's nuclear program has so far been determined by Khamenei, and not by Iran's president," the foreign ministry said after Hassan Rowhani was elected to succeed Mahmoud Ahmadinejad.

Israeli Defense Minister Moshe Yaalon has called for tougher sanctions against Iran over its nuclear program regardless of who is elected as its new president, public radio reported on Saturday.

The report came as partial results from Friday's election gave a clear lead to moderate Hassan Rowhani, who headed Iran's nuclear negotiating team under reformist president Mohammad Khatami in the early 2000s and has pledged to engage more with the international community.

Calling Iran's presidential election a "sham," Canada's top diplomat urged Iranians Thursday to "make their voices heard" by casting protest ballots, boycotting the vote or using satire to express criticism.

"Despite all the efforts of the regime to control the process and the outcome, the hopes and aspirations of the Iranian people are not bound by the artificial choice that the regime has forced on Iranians," Foreign Affairs Minister John Baird said.

Iran's six presidential hopefuls took part in last-ditch election campaigning Wednesday, hoping to woo the millions of Iranians still undecided between a slew of conservatives and a moderate cleric backed by reformists.

Momentum has built for cleric Hassan Rowhani, a former top nuclear negotiator, after the withdrawal of reformist Mohammad Reza Aref on Tuesday, and the endorsement of two ex-presidents, pro-reform Mohammad Khatami and pragmatist Akbar Hashemi Rafsanjani.

Iran's foreign ministry on Tuesday denied its Russian-built Bushehr nuclear power plant had suffered a malfunction, saying the process of its start-up was going ahead without a hitch.

"No problem has been reported at the Bushehr plant. The Russian contractors are overseeing the ongoing and normal process there," ministry spokesman Abbas Araqchi said in remarks reported by Iranian media.