With the apparent failure of Obama’s initiative to open negotiations, the administration turns toward support of the opposition and a focus on sanctions targeting the powerful Revolutionary Guard.

After keeping a careful distance for the last year, the Obama administration has concluded that the Iranian opposition movement has staying power and has embraced it as a central element in the U.S.-led campaign to pressure the country’s clerical government.

Administration officials and some allied governments believe that a combination of domestic unrest and international sanctions targeting Iran’s Revolutionary Guard offers the best hope for forcing Tehran to yield on its nuclear program, and could even lead to a change in the government.

The administration has made the shift at a time when it is facing sharp domestic criticism over President Obama’s failed initiative to launch negotiations with Iran and its perceived unwillingness to strongly back the opposition movement. Meanwhile, the protests sparked by June’s disputed presidential election in Iran grew despite a tough crackdown.

This new approach is not a sure thing: It is far from clear that squeezing the Revolutionary Guard, a sprawling military organization that has vast business interests and is close to President Mahmoud Ahmadinejad, would seriously damage it or strengthen the opposition, as the administration hopes. And despite high-profile encouragement by Secretary of State Hillary Rodham Clinton and other U.S. officials, many opposition activists fear that Washington’s embrace will bring more harm than good.

“Sanctions are increasingly being looked at by the administration in the context of how these measures could be potentially helpful to the cause of political reform in Iran,” said Karim Sadjadpour, an Iran specialist at the Carnegie Endowment for International Peace. “Depriving the Revolutionary Guard of the ability to sign billion-dollar contracts and turning them into an international pariah would be welcomed by many democratic activists in Iran.”

Though U.S. officials have emphasized that they are not trying to overthrow the Iranian government, Vice President Joe Biden and national security advisor James L. Jones have cheered those pressing for a tougher approach by speaking publicly about the prospects for political change.

The new approach does not include formal ties to Iranian dissidents; however, there have been intermittent contacts with some Iranians connected to the opposition.

Administration officials have urged private telecommunications firms to do what they can to enable opposition access to the Internet and other forms of communication.