The Bush administration is taking a calculated risk with its plans to designate Iran's Revolutionary Guard Corps a global terrorist organization. Tehran is certain to see it as a direct challenge to the clerical regime since it's the Guards who keep it in power.

On the other hand, you can't really argue with the accuracy of the designation.

The administration hopes that upping the ante and a stronger U.N. resolution banning travel by Iran's leaders and cutting off access to the international financial system will persuade the Iranians to give up their nuclear-weapons ambitions.

We hope so, but don't count on it. Iran has been under one form of sanctions or another since 1979 without loosening the clerics' grip on power.

The Revolutionary Guards are a separate military branch of 125,000 strong, with its own air and naval capabilities. The group is also a coercive commercial venture, operating many businesses of its own and holding shares of others.

The Guards have been supplying the Shiite militias in Iraq, the Taliban holdouts in Afghanistan and the anti-Israeli Hezbollah in Lebanon and Hamas in Gaza. The Guards are also believed to be the suppliers of explosives used to deadly effect against U.S. forces in Iraq.

The terrorist designation gives the Treasury and State departments leverage to convince foreign firms and financial institutions not to do business with the Guards or invest in their enterprises.

Whatever effect designating the Guards as terrorists has on the Iranians, it responds to demands from Congress for the administration to take a much tougher line on Iran. There's even a small chance it will have the desired effect.