A 60-day period given to Iran by the Security Council to freeze enrichment expired on February 21, exposing Iran to limited UN sanctions that were adopted in December.
UN Secretary-General Ban Ki-moon today expressed "deep concern" over Tehran's failure to comply with the Security Council deadline.
U.S. Secretary of State Condoleezza Rice said earlier today that world powers plan to use all available channels to get Iran to halt its nuclear-enrichment work and start negotiations. She also said Washington has no intention of attacking Iran.
British Prime Minister Tony Blair said he does not know of any planning for an attack on Iran, adding that a diplomatic solution is the only "viable and sensible" answer.
In Iran, at least 100 students rallied in Tehran today in support of the nuclear program. And Iranian President Mahmud Ahmadinejad said Iran will not suspend its research.
The United States has said it plans to seek further Security Council sanctions against Iran.
(compiled from agency reports)