The U.S. announced a new set of Iran sanctions on Tuesday, targeting a network of firms that U.S. officials said were front companies that reap billions of dollars in profits for Iran's top leaders.
The new measures marked the fourth such step in a little more than a week, reflecting a renewed U.S. determination to constrict the Iranian economy.
But they weren't enough to convince skeptical lawmakers at a Senate Banking Committee hearing on Tuesday that sanctions would force Iran to curtail its nuclear program.
The main problem, some experts said, is that Iran's reserves of foreign currency could enable it to weather another year of economic turmoil while accelerating its weapons development.
"Nuclear physics is beating Western economic pressure," said Mark Dubowitz, executive director of the Foundation for the Defense of Democracies, a group that favors increased sanctions on Iran. "Although sanctions are denying the regime lots of hard currency, they are still too weak to crack the nuclear will of the regime."