Secretary of State Hillary Clinton says the United States may call for "stricter sanctions" against Iran if U.S. diplomatic efforts with Tehran fail.
Clinton commented late Tuesday in an an exclusive interview with Venezuela's Globovision TV.
She responded to a question about how she perceived relations between Iran and Venezuela by saying "Iran has not respected its own democracy."
The Secretary of State referred to Iran's crackdown on demonstrators who opposed the results of the June presidential elections, which gave the victory to incumbent President Mahmoud Ahmadinejad.
Clinton also said the U.S. is concerned about Iran's effort to develop nuclear weapons, which she says could destabilize the Middle East. Iran has long maintained that its nuclear program is intended to produce electricity.
Clinton said if the "policy of careful engagement" with Iran failed, the U.S. may "ask the world" to join in imposing more sanctions.
Iran has already been hit with three sets of United Nations sanctions for its refusal to stop enriching uranium, a process that could be used to develop nuclear weapons.
Meanwhile, the political crisis in Iran is among the issues expected to be discussed Wednesday at a meeting in Italy of leaders of the world's eight major industrial countries.
U.S. President Barack Obama is attending the G-8 meeting, which also includes Germany, Japan, France, Britain, Italy, Canada and Russia.