The European Union and Canada have imposed new sanctions against Iran that target the country's energy, foreign trade and banking sectors.
Their sanctions aim in part to curb investment and trade in Iran's lucrative oil and gas industries.
EU foreign policy chief Catherine Ashton said the sanctions send a powerful message to Iran that its nuclear program is a cause of "serious and growing" concern. But she said sanctions are not the sole solution to the Iranian nuclear dispute, and that the EU goal remains to persuade Iran to return to the negotiating table.
The sanctions are the latest measures taken by the international community to punish Iran for its refusal to stop enriching uranium. In recent weeks, the U.N. Security Council imposed a fourth round of sanctions against Iran, and the United States approved its own economic measures.
The new EU sanctions also bar Iran's shipping and air cargo companies from operating in EU territory. They go beyond the fourth round of sanctions imposed by the U.N. Security Council.
In related news, the International Atomic Energy Agency says it has received a letter from Iran's government about providing nuclear fuel for an Iranian medical research reactor. Iran's state-run news agency IRNA says Iran's envoy to the IAEA, Ali Asghar Soltanieh, will reveal details of the request at a later date.
The IAEA said the request was passed on to the Vienna group - Russia, France and the United States - along with Turkey and Brazil.
The United States and its allies accuse Iran of using its civilian nuclear program as a cover to develop atomic weapons. Iran denies the charge.
Some information for this report was provided by AP and AFP.