Michael A. Levi, David M. Rubenstein Senior Fellow for Energy and the Environment and Director of the Program on Energy Security and Climate Change
People love to talk about "red lines" for all sorts of challenges, and the Iranian nuclear program is no exception. The United States can, in principle, threaten stronger sanctions if Iran crosses certain red lines. It can threaten military action if Iran crosses others. But it's not clear that setting red lines—particularly in public, where failing to follow through on threats can be costly—is a productive course.
If the United States or other leaders do, however, want to set red lines, they would do well to keep two basic principles that I laid out in a 2011 paper in mind. Red lines should be set such that violations are relatively straightforward to detect. They should also be carefully calibrated with the threatened response, ensuring that whatever action the United States takes has enough time to stop Iranian progress before Tehran actually acquires a bomb.