Iran has invited Russia, China, the European Union and its allies among the Arab and developing world to tour its nuclear sites.
The invitation is contained in a letter made available to The Associated Press. It appears to be a move to gain support ahead of a new round of talks with the US, and five other world powers.
In the letter, senior Iranian envoy Ali Asghar Soltanieh suggests the weekend of January 15 and 16 for the visit.
He said that meetings "with high-ranking officials" were envisaged.
The offer comes just weeks before Iran and the six powers follow up on recent talks that ended with agreement on little else but to meet again.