Thomas Selzer, the president of the UN preparatory commission on the implementation of the Comprehensive Test Ban Treaty (CTBT), said it would be a logical step as Iran appeared ready to heed other calls on its nuclear programme.
"Iran, which now appears ready to sign an additional protocol to the Non-Proliferation Treaty (NPT), should ratify the CTBT. It is logical," he said.
Iran, which denies that it is seeking to develop nuclear weapons, signed the CTBT in September 1996, but has so far failed to ratify the treaty.
The treaty commits countries who have ratified to refrain from any kind of nuclear weapons testing.
The treaty appears likely to collapse as all the countries with nuclear capabilities must ratify it in order for it to come into force, and the United States has indicated that it has no plans to ratify it.
Under strong international pressure Iran recently announced that it was prepared to sign an additional protocol to the NPT that would allow surprise inspections of its nuclear sites.
It is expected to do so after a meeting of the UN nuclear watchdog, the International Atomic Energy Agency (IAEA), in Vienna on November 20.
The IAEA this week in a report accused Tehran of two decades of covert nuclear activities, including making plutonium and enriched uranium, but said it had found no evidence that the Islamic Republic was pursuing a nuclear weapons programme.