The United States and France said Monday they would push for new UN sanctions against Iran over its nuclear programme after Tehran announced it was going to enrich uranium to a higher level.

Western powers condemned the move, which Germany said was a sign that Iran is not cooperating with the international community, which wants the fuel to be upgraded abroad.

A top Russian lawmaker called Tehran's move "a sure step backward" and said new sanctions should be discussed -- a step Moscow has previously opposed.

Iran on Monday officially informed the UN International Atomic Energy Agency (IAEA) that it planned to start enriching uranium to 20 percent on its own from Tuesday.

Western countries fear its nuclear programme masks plans to build an atomic bomb, a charge rejected by Tehran which insists its activities are strictly for energy purposes.

French Defence Minister Herve Morin, speaking after Paris talks with US Defence Secretary Robert Gates: "We have no choice but to work on other measures."

Morin, whose country holds the rotating chair on the UN Security Council, added: "It will unfortunately be necessary to launch a dialogue with the international community that will lead to new sanctions if Iran does not stop its programmes."

Gates, whose aides had earlier said the United States would ask France to submit a sanctions motion, said: "We are very much agreed that action by the international community is the next step."

Iran's move raises the stakes in a long-running dispute with the West less than a week after it had signalled it favoured a UN-drafted agreement on the supply of fuel for a research nuclear reactor in Tehran.