By Crispian Balmer

PARIS (Reuters) - Iran will redouble efforts to build an atomic bomb following Mahmoud Ahmadinejad's victory in a presidential election but could still be deterred by tough sanctions, the head of an exiled Iranian group said Saturday.

Maryam Rajavi, leader of the French-based National Council of Resistance of Iran (NCRI), told Reuters that Western powers had to abandon a "policy of appeasement" if they wanted to thwart Ahmadinejad's nuclear ambitions.

"Sadly Iran will get the bomb if the West continues with its strategy of negotiations. This is just giving the mullahs more time to play with," she said in a telephone interview.

"Lots of sources say they will get the bomb in 1-1/2 years, but Ahmadinejad will now speed things up and he will have the bomb in one year maximum."

The NCRI has thousands of followers in Europe and the United States and was the first group to expose Iran's covert nuclear program in 2002. It claims to have huge backing within Iran although analysts say its support is very hard to gauge.

Iran's interior minister said Saturday that hard-liner Ahmadinejad swept Friday's presidential election with 62.6 percent of the vote. Turnout was put at a record 85 percent.

Rajavi called the election "a charade" and said most Iranians had shunned the ballot boxes.

"Around 85 percent of people boycotted this election. It is not true there was a massive turnout," she said, adding there was growing public anger over the vote.

"The situation is explosive ... The mullahs are afraid."

CLASHES

A Reuters witness in Tehran reported that Ahmadinejad partisans clashed Saturday with about 2,000 supporters of moderate former prime minister Mirhossein Mousavi, who came second in the election after initially claiming victory.

Many in the West had high hopes in Mousavi but Rajavi said the United States and its allies had misread the situation. Moderates would never be given power in Iran while Supreme Leader Ayatollah Ali Khamenei held sway, she said.

"Sadly Western authorities are trying to find moderates in the mullah regime. But it is wrong to think one can negotiate with the mullahs," she said. "The (nuclear) negotiations are dead in the water."

The United States, Russia, China, France, Germany and Britain have invited Iran to talks to find a diplomatic solution to the nuclear row, but Tehran has so far rejected the offer.

The major powers suspect Iran wants to produce a nuclear weapon. Tehran says it wants to generate electricity.

"The West can stop the nuclear program if they stand up to the mullahs. They need strong sanctions, generalized sanctions on oil, on the economy and political sanctions," said Rajavi.

The U.N. Security Council has imposed several rounds of sanctions on Iran.

The main faction within the NCRI opposition umbrella movement is the People's Mujahideen Organization of Iran (PMOI), based in Iraq. European states agreed this year to remove it from a list of banned terrorist groups but Rajavi said much of its bank funds remained frozen despite the decision.

"This makes things very difficult for us," she said.

(Editing by Robert Woodward)

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