A report published Monday by the Washington Post says Iran and Lebanon's Hezbollah have been building a militia network in Syria to preserve their interests if President Bashar al-Assad's government collapses.
Citing unnamed senior U.S. and Middle Eastern officials, the report says the militia's immediate goal is to support Mr. Assad's military as it battles rebel forces in a civil war that is approaching its third year.
But the officials say the long-term goal is to have a reliable presence in Syria in the event the government collapses or is forced to retreat from Damascus.
A senior Obama administration official was quoted as saying "It is important for Iran to have a force in Syria that is reliable and can be counted on."
Neither Iranian nor Hezbollah officials have commented on the report.
The United Nations says more than 60,000 people have died since the Syrian conflict began in March of 2011.
On Monday, activists in Syria said rebels had taken hold of the country's largest hydro-electric dam along the Euphrates River in the northern province of Raqa. The Syrian Observatory for Human Rights said the dam is still in operation.
Government and rebel accounts cannot be independently verified because Syria does not permit journalists to report freely.