The UN Secretary General, Kofi Annan, is to visit Iran on Saturday, two days after a Security Council deadline for a freeze on sensitive nuclear fuel work there.
In Washington, there was muted reaction to the news that Iran's president had inaugurated a facility producing coolant for nuclear reactors.
The White House said only that it would take into account Iran's activities when the Security Council next meets.
Iran insisted that it would never stop uranium enrichment despite a looming UN deadline intended to ensure it cannot develop atomic weapons.
