Derailing Iran’s drive to build nuclear weapons is too important a goal to let fantasies interfere. The point of intricate diplomacy now getting underway is not to punish the Iranians with sanctions or overthrow the Islamic republic but to terminate its nuclear enrichment programmes before they reach the point where Iran can produce nuclear weapons.

That is a goal that all five permanent members of the UN Security Council share, and one they have a chance to achieve if they take a united and tough stand. The next few weeks will determine whether unity can be preserved without sacrificing toughness. The decisive factor will be how Russia plays its pivotal hand. It needs to play an active role in convincing Iran that it must renounce its efforts to develop a fully independent nuclear enrichment cycle.

The US and Europe are not asking the Security Council to impose economic sanctions. What they want is a statement or resolution that backs up the IAEA’s authority and sends Iran a united message that its current course is dangerous and unacceptable. And if China joined these actions as well, the chances of achieving a successful dipl-omatic resolution would be still greater. If Russia and China are the champions of multilateral nuclear diplomacy they have long clai-med to be, now is the time to show it.