The United Nations Security Council this week passed a resolution that gives Iran a stark choice: suspend its uranium-enrichment activities or face possible economic sanctions. The move is a victory for those who fear that Iran's nuclear programs threaten to unravel the global nuclear nonproliferation regime, as well as for those who seek a strong U.N. that is capable of responding to international security threats. Failure to act would confirm the argument that the world body has become irrelevant.

While the resolution is welcome, it is only a first step: Iran must return to the negotiating table, and negotiate in good faith, or the U.N. must be prepared to sanction Tehran.

There has been mounting alarm over Iran's nuclear activities. Tehran insists that it is merely exercising its right as a member of the Nuclear Nonproliferation Treaty (NPT) to develop a peaceful nuclear-energy program. That means carrying out all facets of the nuclear-fuel cycle -- including uranium enrichment and nuclear-fuel reprocessing, which can also be used to develop a nuclear bomb.