Hossein Naqavi-Hosseni, a spokesman for the Iranian National Security and Foreign Policy Committee, said Tehran has offered "maximum cooperation" with the International Atomic Energy Agency and members of the P5+1 -- Britain, China, France, Russia and the United States plus Germany.
"Despite this, (Iran) does not see real determination in the P5+1 to resolve the nuclear case," he was quoted by state-funded broadcaster Press TV as saying.
Members of the P5+1 have called on Iran to halt production of uranium enriched to 20 percent, which Iran says it needs for medical research. Western powers, however, say it's a benchmark that would make it easier to reach the 90 percent purity needed for a nuclear weapon.
U.N. nuclear inspectors left Iran last month without gaining access to the Parchin military complex outside of Tehran. The International Atomic Energy Agency there were questions about the peaceful nature of nuclear activities there.
Both sides agreed to resume negotiations Jan. 16.