A senior U.S. envoy said Wednesday, March 6 Iran is committed to "deception, defiance and delay" in how it deals with international concerns about its nuclear program.

The hard-hitting comments by the chief U.S. envoy to the International Atomic Energy Agency, Joseph Macmanus, to the 35-nation board of the IAEA reflect U.S. frustration over Iran's expanding uranium enrichment program and stalled attempts by the UN's nuclear agency to probe suspicions that Tehran might have tried to develop nuclear weapons in secret.

Iran denies any such efforts and says all its nuclear activities are peaceful. But it continues to block IAEA experts access to sites, officials and documents it wants to probe and refuse the UN Security Council demands to stop enrichment, which can be used to make reactor fuel and fissile warhead material.