Washington and its allies are preparing new "significant" sanctions against Iran over its nuclear program, U.S. President Barack Obama said on Tuesday.

His statement came after Iranian state media said the Islamic Republic had begun enriching uranium to 20%.

Speaking in the U.S. capital, Obama said the world was "unified around Iran's misbehavior in this area."

"They have made their choice so far, although the door is still open," Obama told journalists in the White House briefing room.

Western powers suspect Iran of aiming to build a nuclear weapon. The Islamic Republic has consistently said its program is designed toward the peaceful generation of power.

Obama also said he was pleased by Russia's "forward-leaning" statements on the issue of Iran.

In a sign that Russia, a traditional Iranian ally, is moving closer and closer to the position of Western nations, the Russian Foreign Ministry said on Tuesday it was "disappointed" by Iran's decision to enrich uranium to 20%.

But Obama noted that China's response to calls for sanctions at the UN Security Council was "something we're going to have to see."

The UN Security Council's five permanent members - the U.S., Russia, China, France and Britain - have the power to veto resolutions, including sanctions.

MOSCOW, February 9 (RIA Novosti)