Western intelligence officials told the British Telegraph on Thursday that Iranian President Mahmoud Ahmadinejad has personally sanctioned the dispatch of the experienced officers to ensure that the Assad regime survives the threat to its survival.

According to the report, Iran has also shipped hundreds of tons of military equipment, including guns, rockets, and shells to Syria through the regular air corridor that has been established between Damascus and Tehran.

Intelligence officials believe the increased Iranian support has been responsible for the growing effectiveness of the Assad regime's tactics in forcing anti-government rebel groups on the defensive.

In the past few weeks, the Telegraph noted, pro-Assad forces have seized the offensive by launching a series of well-coordinated attacks against rebel strongholds in Damascus and Aleppo.

The Iranian operation to support Assad is being masterminded by Qassem Suleimani, the head of the Guards' Quds force which is responsible for overseeing Iran's overseas operations. The decision to increase Iran's support for Syria was taken after the Syrian defense minister and Assad's brother-in-law were killed in a suicide bomb attack at Syria's national security headquarters in July, together with a number of other senior defense officials.

The Revolutionary Guards officers were flown to Damascus in chartered Iranian aircraft which were given permission to fly through Iraqi air space, said the report. Iranian military equipment is said to have been shipped to Syria by the same route.

A spokesman for the National Council of Resistance in Iran (NCRI) told the Telegraph that some of the Iranians being held by Syrian opposition groups included several brigadier-generals and a number of colonels who had many years of experience serving in the Revolutionary Guards.

"Iran has taken a strategic decision to deepen its involvement in the Syrian crisis," a senior Western security official told the newspaper. "The Iranians are desperate for their most important regional ally to survive the current crisis. And Iran's involvement is starting to pay dividends."

Iran publicly confirmed last week that its government has sent elite Revolutionary Guards to support the troops of Syrian President Bashar al-Assad in that country's civil war.

Commander General Salar Abnoush told a group of volunteer trainees during a speech, “We are involved in fighting every aspect of a war – a military one in Syria, and a cultural one as well.”

On Saturday, a senior official in the Iranian Revolutionary Guards threatened the United States and its allies that the Islamic Republic would respond harshly to a “stupid” attack on Syria.

The quotes, which were published on an official government-linked news agency, were removed a few minutes after being posted, but not before the BBC’s Persian-language website copied them and republished them.

The comments were made by Mohammad Ali Assoudi, the deputy for culture and propaganda of the Islamic Revolutionary Guard Corps.

“If the United States carries out the stupid act and attacks Syria, Iran and Syria’s allies in the world will react strongly and will turn America into a fiasco,” Assoudi said.

He did not specify what courses of action Iran would take, but stressed that there is a military alliance between the two countries that would require Iran to respond.