A senior Iranian lawmaker says his country has begun installing 3,000 centrifuges to speed up its controversial nuclear program.
Iran's state news agency (IRNA) quotes the head of foreign affairs and national security committee, Alaeddin Boroujerdi, as saying the devices to enrich uranium are now being installed.
On Friday, U.S. Undersecretary of State for Political Affairs Nicholas Burns said Iran would risk another punitive U.N. Security Council resolution if it installed the devices.
Earlier this week, Iran barred 38 U.N. nuclear inspectors who came from nations responsible for a Security Council sanctions resolution.
The Security Council imposed sanctions last month after Iran refused to suspend uranium enrichment, which can be used to produce nuclear weapons.
Britain, France and Germany drafted the resolution with the support of the United States.
The Western powers believe Iran is trying to develop nuclear weapons, but Iran says its nuclear program is for peaceful purposes.
Some information for this report was provided by AFP and Reuters.