SCOTT JAGOW: The Treasury Department has frozen the American assets of four Chinese companies and one US firm. They're accused of selling missile parts to Iran. The government also barred other companies from doing business with them. Ashley Milne-Tyte explains the strategy.

ASHLEY MILNE-TYTE: Clamping down on companies it does business with is a non-controversial way to hit Iran.

Consensus for military action is low, and William Overholt of the Rand Corporation says, although broad economic sanctions are under discussion . . .

WILLIAM OVERHOLT: Countries like India and Russia and China still don't think they're appropriate, so the administration is doing things that are directly targeted at the weapons problem.

He says it's hard to say how effective this move will be. The targeted companies may be able to take some of their business elsewhere. Still, he says, the US is sending a signal that it's serious about curbing Iran's military capabilities, and that further action may be on the way.

I'm Ashley Milne-Tyte for Marketplace.