The U.S. national security adviser says Washington is still open to nuclear negotiations with Iran, but the picture is not a "good one."
Jim Jones said Sunday the "clock is ticking" toward the end of the year, when President Barack Obama plans to review U.S. diplomatic efforts with Iran.
Senior U.S. officials have proposed pursuing new sanctions at the U.N. Security Council if Iran does not cooperate with the international community on its nuclear program.
The United States and other world powers suspect Iran is developing nuclear weapons. Tehran says its program is peaceful.
Iranian Supreme Leader Ayatollah Ali Khamenei accused world powers Sunday of lying about Tehran's nuclear program to isolate the country.
Iran recently announced plans to build 10 new uranium enrichment plants.
General David Petraeus, the head of the U.S. Central Command, said Sunday a lot of experts have questioned Iran's ability to do that.
But, he said, Iran's recent activity has caused enormous worry and concern.