Iran is secretly helping Syrian President Bashar al-Assad put down pro-democracy demonstrations, according to U.S. officials, who say Tehran is providing gear to suppress crowds and assistance blocking and monitoring protesters' use of the Internet, cellphones and text-messaging.

At the same time, communications intercepted by U.S. spy agencies show Tehran is actively exploring ways to aid some Shiite hardliners in Bahrain and Yemen and destabilize longstanding U.S. allies there, say U.S. officials familiar with the intelligence. Such moves could challenge interests of the U.S. and Saudi Arabia and inflame sectarian tensions across the Middle East, they say.

"We believe that Iran is materially assisting the Syrian government in its efforts to suppress their own people," said an Obama administration official.

U.S. officials say they don't see Iran as the driving force behind popular revolts against longtime U.S. allies in the Mideast, and caution they have no concrete evidence that Iran is providing or preparing large-scale financial or military support to opposition elements in Bahrain or Yemen.

Rather, the White House has worried that protracted political turmoil could provide an opening for additional influence by Tehran, whose nuclear ambitions are a concern to the U.S. and its allies in Europe and the Middle East.

So far, an administration official said, Iranian "aspirations far outpace their ability to project their influence into these places."

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