President Bush has made a direct appeal to the Iranian people, telling them the United States respects them and their country, but Iran's rulers are denying them liberty.
Speaking before the United Nations General Assembly Tuesday, Mr. Bush said Iran's leaders are using the nation's resources to fund terrorism and pursue nuclear weapons.
The president said the United States continues to seek a diplomatic solution to the nuclear standoff with Iran.
In his address on Tuesday evening, Iran's President Mahmoud Ahmadinejad defended his country's nuclear program, calling it transparent and peaceful.
The Iranian president also accused some permanent members of the U.N. Security Council -- an apparent reference to Britain and the Untied States -- of exploiting the international body for their own agendas.
Earlier, Thailand's Prime Minister Thaksin Shinawatra canceled his scheduled address before the General Assembly, hours after the Thai military staged a coup in Bangkok.
Also Tuesday, U.N. Chief Kofi Annan opened his last General Assembly session as secretary general, saying major global challenges have sharpened during his decade-long tenure.
Mr. Annan cautioned against the threat of weapons of mass destruction and called for non-proliferation and disarmament.