The International Atomic Energy Agency says Iran will not get an extension of the October 31 deadline to clear up all questions regarding its nuclear ambitions.
The head of the IAEA, Mohamed ElBaradei, left for Tehran for high level talks with Iranian officials.
The U.N. nuclear watchdog has given Iran until the end of the month to prove that its nuclear program is not geared to making nuclear weapons. Mr. ElBaradei says the deadline is non-negotiable.
Agency spokesman, Mark Gwozdecky, said Iran has given some information, but not enough. "But we need them to move more quickly, particularly to help us resolve some very serious questions around their enrichment program; what its history is and what testing procedures there have been, where components and equipment were sourced, this sort of thing we need to get to the bottom of very, very quickly," he said.
Iran has provided the IAEA with a list of components, but says it cannot give details on the suppliers.
This week an opposition Iranian exile group gave the IAEA information on what it claims are more secret nuclear sites in Iran. The IAEA says it is examining the material and may want to visit more sites in Iran, if necessary.
The IAEA board of governors meets at the end of November and has the power to pass the Iran file on to the U.N. Security Council.
Diplomats say the IAEA does not want to turn over the matter to the Security Council completely, but may just want the Council's support for its own investigation.
A diplomat from a non-western country, who asked not to be named, said Iran is not acting in defiance of international norms as was the case with North Korea. He said several countries on the IAEA board had been unhappy with the idea of a deadline in the first place, because it gave the impression that Iran need not cooperate after October.
The diplomat said the deadline itself is subject to several interpretations.