Russia and the European Union have joined the United States in condemning Iran's nuclear program, one day after Tehran said it had succeeded in enriching uranium to a level used in nuclear power plants.
Russia and Germany are calling the Iranian development a step in the wrong direction, and France has urged Iran to stop what it called dangerous activities.
Israeli elder statesman Shimon Peres called Iran's claim worrying and frustrating, but said diplomacy is the best way to resolve Iran's nuclear standoff with the West.
Iran's announcement of progress toward industrial-scale production of uranium fuel came in the middle of a 30-day period set by the U.N. Security Council for Tehran to cease all nuclear work.
The head of the International Atomic Energy Agency, Mohamed ElBaradei, was scheduled to arrive in Iran Wednesday for talks on the dispute. He is to brief the Security Council after the U.N. deadline expires April 28th.
On Tuesday, the United States renewed its call to Tehran to stop its nuclear work and heed the will of the international community.
Despite Iran's technical breakthrough, experts say Iran has a long way to go before it would be able to produce a nuclear weapon.
However, some analysts say Iran's announcement could prompt the U.N. Security Council to consider sanctions or other harsh measures against Tehran sooner than previously expected.