Iranian President Mahmoud Ahmadinejad has rejected a U.N. Security Council resolution giving his country until the end of the month to suspend sensitive nuclear work.
Mr. Ahmadinejad says Iran will not be forced to give up what he says is its right to a peaceful nuclear program.
On Monday, the Security Council approved the resolution that says Iran could face possible sanctions if it fails to suspend uranium enrichment.
China and Russia voted for the resolution, saying they hope its passage will lead to a diplomatic solution to the Iranian nuclear standoff. But Iran's U.N. ambassador, Javad Zarif, said it will only worsen the situation.
President Bush said Iranians must hear "loud and clear" that the world is intent on working together to make sure Tehran does not get a nuclear weapon.
Sanctions could include a ban on the import of materials and technology that could be used for nuclear activities, as well as travel restrictions on Iranian leaders.
The U.S. and its Western allies believe Iran is trying to develop nuclear weapons. Tehran says its nuclear program is only for peaceful purposes.
Some information for this report was provided by AFP, AP and Reuters.