As many as 50,000 militiamen backed by Iran and Lebanon's Hezbollah Shiite Islamic militant group and political party are being cultivated inside Syria to preserve and protect Tehran and Hezbollah's interests in a post-Assad Syria, the U.S. and Middle Eastern officials told the newspaper.
"It's a big operation," a senior Obama administration official told the Post. "The immediate intention seems to be to support the Syrian regime. But it's important for Iran to have a force in Syria that is reliable and can be counted on."
A senior Arab official agreed Iran's strategy has two tracks.
"One is to support Assad to the hilt -- the other is to set the stage for major mischief if he collapses," the official said.
The focus of the Islamist militias, some reputed to have ties to al-Qaida, contrasts with the fragmentation of the rebels seeking to overthrow Assad, the Post said.
Some militia groups are receiving military training from officers from Hezbollah and the secretive Quds Force of Iran's Islamic Revolutionary Guard Corps, an elite military unit tasked with "exporting" Iran's Islamic revolution, the Post said.
The Quds Force has a history of carrying out activities in other countries, including the training and arming of the Hezbollah militia in Lebanon, The New York Times says.
The Quds Force reports directly to Iranian Supreme Leader Ayatollah Ali Khamenei.
In October 2011, U.S. Attorney General Eric Holder announced U.S. authorities had foiled a plot by men linked to Tehran and the Quds Force to assassinate Saudi Arabia's ambassador to the United States and to bomb the Israeli and Saudi embassies in Washington.
"The president and I spoke about this visit and agreed that we would discuss three main issues -- Iran's attempt to arm itself with nuclear weapons, the unstable situation in Syria and the efforts to advance the diplomatic process of peace between the Palestinians and us," Netanyahu said.