Iran plans to give a formal response Tuesday to the West's offer of incentives if it freezes uranium enrichment.
Iran's supreme leader, Ayatollah Ali Khamenei, said Monday Iran will pursue its nuclear work despite the threat of United Nations sanctions.
Ayatollah Khamenei said Iran has made its decision and with patience and power, will continue along the path towards nuclear energy.
The United States and much of Europe accuse Iran of planning to build nuclear weapons - a charge Tehran denies.
The U.N. Security Council has imposed an August 31 deadline for Iran to suspend enriching uranium or face sanctions.
President Bush said Monday he hopes the council will take quick action.
Meanwhile, international nuclear inspectors say Iran denied them access to part of a nuclear fuel plant during a regular inspection last week.
Some information for this report was provided by AP and Reuters.