Iran has rejected a call from a UN agency to stop enriching uranium and related programs.
On Saturday, the International Atomic Energy Agency (IAEA) demanded the country stop because enriched uranium can be used to make nuclear weapons.
The IAEA resolution said it would decide on Nov. 25 whether Iran had meet the demand.
Hasan Rowhani, Iran's top nuclear negotiator, on Sunday denounced the IAEA action.
"This demand is not legal and does not put any obligation on Iran. The IAEA board of governors has no right to make such a suspension obligatory for any country," he said.
Iran has voluntarily suspended enriching uranium, but will continue related activities, Rowhani said.
"We are committed to the suspension of actual enrichment but we have no decision to expand the suspension," he said.
The U.S. believes Iran is trying to make nuclear weapons; Iran says its nuclear program is designed to produce energy.
The U.S. wants the IAEA to refer Iran to the UN Security Council, which can apply sanctions.
If that happens, Iran will end its commitment to stop enrichment and stop co-operating with the IAEA, Rowhani said.
Iran has agreed to let inspectors examine its nuclear program.