Last month, George W. Bush, US president, took steps to heal the trans-Atlantic breach, including reaffirming support for a strong Europe. While serious differences remain, these steps laid a foundation to repair a frayed relationship. Now Moscow has signed an important deal requiring Tehran to return to Russia all spent fuel produced in the Bushehr nuclear reactor. Together, these events create an opportunity to contain the Iranian nuclear threat.

For more than a decade, the US has urged Russia to refrain from dangerous nuclear exports to Iran. Russia has proceeded with construction of the Bushehr nuclear reactor but in recent years has halted the kind of aid that would help Iran enrich uranium or separate plutonium. By refusing to send fresh fuel to Bushehr until Tehran agreed to give back all of the plutonium-laced spent fuel, Russia has denied Iran a pathway to nuclear weapons capability.