Qasem Soleimani, head of the Iranian Revolutionary Guards Corps elite Quds force, was in the Syrian capital this month, one official said, in what Washington sees as the most concrete sign yet that Iranian aid to Syria includes military hardware.
"We are confident that he was received at the highest levels of the Syrian government, including by President Assad," the official said on condition of anonymity.
"We think this relates to Iranian support for the Syrian government's attempts to suppress its people."
The official said Washington has reason to believe that Iran is supplying security-related equipment "including munitions" to Syrian forces.
"The US government believes Iran has supplied Syria with munitions" for use in the military crackdown, he said.
The United States has long suspected that Iran has been aiding Syria's purge against protesters as Assad tries to cling to power and avoid the fate of other Arab dictators felled by the Arab Spring uprisings.
Another official said Soleimani's visit marks the strongest indication yet of direct cooperation between the allies amid a purge that the UN estimates has left more than 5,000 people dead since March.
The officials did not give further details of the information that has led them to conclude that Tehran has indeed provided security equipment and munitions to the Syrian armed forces.
The powerful Soleimani has been mentioned by some observers as a possible successor to Iran's President Mahmoud Ahmadinejad and has repeatedly been the target of US sanctions.
Washington last year accused him of links to an alleged plot by the Quds force to kill the Saudi ambassador to Washington by hiring assassins from a Mexican drug cartel for $1.5 million.
The latest revelations come with the United States locked in a tense standoff with Tehran over its nuclear program and as maritime tensions between the two states simmering in the Strait of Hormuz, a vital oil shipping route.
Washington has warned Iran it will not tolerate any attempt to close the Strait, as Tehran becomes increasingly infuriated by the growing impact of US and international sanctions designed to deter its nuclear program.
The Revolutionary Guards maritime division, which handles military operations in the strait and the Gulf, is expected to hold maneuvres in the area soon.
Signs of direct cooperation between Iran's Revolutionary Guards and Syria came a week after Mahmud Suleiman Haj Hamad, a former official in Assad's regime, accused Iran and Iraq of financially aiding the Syrian crackdown.
He made the allegations at a press conference in Cairo after announcing his defection from the regime, according to an Al-Jazeera report.
Iran has also been standing firm with Syria after the Arab League suspended Damascus over the repression wracking the country and imposed fierce pressure on the Assad regime to accept a peace plan.
Tehran has been concerned about the possible collapse of Syria, its principal regional ally, a scenario that would leave it even more isolated in its own region as nuclear sanctions bite.
It has accused its traditional foes Israel and the United States of stirring up trouble in Syria.
In a televised speech lasting nearly two hours on Tuesday, Assad vowed to crush "terrorism" with an iron fist and accused outsiders of trying to destabilize his country.
That prompted opposition movements to accuse him of pushing Syria towards civil war and world powers to accuse him of trying to shift the blame for the 10 months of bloodletting in the protests against his regime.
Secretary of State Hillary Clinton described the speech as "chilling" and the United States says Assad has long since lost political legitimacy after oppressing the hopes of Syrians for freedom and democracy.
COMMENTS (9)
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Iran is supporting Syrian Alwite/Shia regime, who rules over majority Sunni population. Whereas Saudi and other Sunni Arabs sent forces (not just munitions) to Bahrain which is ruled by Sunni king with Shia majority population. Same Difference. Mubarak of Egypt and Ben Ali of Tunisia were relatively smart and left power before things got too bad. Tunisia has an elected government already and Egypt is in the process. Kadhafi could have done the same. Now it is time for Kalifa family and Al Asad to leave their thrones before all out civil wars there. However being rational, one must admit that Iran and Syria also assists Sunni Hamas and Shia Hizbollah both with humanitarian and military aid. Gaza and South Lebanon are free of Israeli boots because of that assistance.
@Pakistani
The article is written by AFP not ET reporters. The allegations of arms delivery are not baseless as they originate from Turkey which has intercepted and turned back several shipments.
Both Iran and Syria face sanctions and international isolation. They need each each other to weather the storm and give one another moral support. The visists are a token of solidarity. Besides Bashar al-Assad expects more unrest in the coming weeks and months.
@Jadugar: Was it not that the Americans supplying arms and war planes to Pakistan, I wonder why?
The double standard practised by the US and the European countries in the Middle East revolution are all to clear, If they are trying to potray the Syrian and Iran as bad people, their propaganda is not working. Isnt the Americans supplying Anti Missle in hundreds and troops to Isreal, I wonder Why
USA making war between groups and countries and selling arms to the whole world, GOOD BUSINESS for USA...
ET is too much US pro
............astonishing, the things a superpower can do in the name of democracy.