Iranian officials have reportedly told a top British newspaper that Tehran and its ally Syrian President Bashar Assad have won the over three-year war between Damascus and opposition forces.

Senior Iranian political figures have said the West's strategy to support rebel groups opposed to the Syrian regime has failed and backfired, the Guardian reported on Monday.

In a series of interviews conducted by the Guardian, top Iranian figures claimed that US attempts to bolster opposition forces in Syria have prompted radicals and increased chaos plaguing the country.

"We have won in Syria," Alaeddin Boroujerdi, Chairman of the Iranian Parliament's National Security and Foreign Policy Commission was quoted as saying.

"The regime will stay. The Americans have lost it," he claimed. 

According to the Guardian, Boroujerdi said with the government in Damascus secured, Sunni jihadist groups and individuals now posed the main threat to Syria.

More than 150,000 people have been killed in the Syrian conflict, which has become increasingly sectarian as rival regional powers have backed either Assad, a member of the Shi'ite offshoot Alawite sect, or the overwhelmingly Sunni rebels who oppose him.

Iran and Russia have been Assad's strongest supporters during the crisis and world powers have called from them to exert pressure on the Syrian government for humanitarian deals.

Shi'ite Iran has already spent billions of dollars propping up Assad in what has turned into a sectarian proxy war with Sunni Arab states.

Another Iranian government advisor told the Guardian that the US had erred in seeking to topple Assad without proposing a viable alternative rule.

"We won the game in Syria easily. The US does not understand Syria. The Americans wanted to replace Assad, but what was the alternative?" Amir Mohebbian said.

During the interviews, Iran's Deputy Foreign Minister Majid Takht-Ravanchi charged that Syria's main priority now was to restore stability ahead of presidential elections schedule for June 3, and for Assad's alleged victory to be accepted.

"Extremism and turmoil in Syria must be tackled seriously by the international community. Those countries that are supplying extremist forces must stop helping them," he said.

Reuters contributed to this report.

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