Iran under the terms of an interim agreement set to enter into force next week curbs some of its nuclear activity in exchange for relief from some Western economic sanctions.
Ali Akbar Salehi, director of the Atomic Energy Organization of Iran, said enrichment activity would continue during the six-month duration of the interim deal.
"We have voluntarily agreed to suspend only the 20 percent enrichment in this six-month period but this suspension does not mean the centrifuges for 20 percent enrichment will stop working," he was quoted as saying Wednesday by Iran's state-funded broadcaster Press TV.
Instead, Salehi said Iranian centrifuges would enrich uranium to 5 percent purity. Enrichment to 20 percent purity is seen as a breakthrough in the possible development of a nuclear weapon.
White House spokesman Jay Carney said during a Wednesday press conference Washington was working to ensure Iran never develops a nuclear weapons program.
"[President Barack Obama] retains all options, including military options, to fulfill his policy goal," he said. "But it is absolutely preferable to him, to the American people, and to all those who demand that Iran forsake nuclear weapons that this be resolved peacefully."