President Bush is on his way to Vienna for talks Wednesday with European Union leaders on Iran's nuclear program, terrorism and trade.
The Europeans also are expected to raise the issue of closing the U.S. military detention facility at Guantanamo Bay in Cuba.
White House National Security Adviser Stephen Hadley says promoting freedom and democracy and winning the war on terror top Mr. Bush's agenda.
The meeting is to review the major powers' efforts to resolve the dispute over Iran's nuclear program, but no major announcements on that topic are expected.
Iran is currently considering an incentives package to stop sensitive nuclear work.
Mr. Bush says a nuclear-armed Iran would pose a grave threat to all people, but adds that Iran will see real benefits if it verifiably suspends uranium enrichment and reprocessing activities.
The president, who spoke Monday at the U.S. Merchant Marine Academy in Kings Point, New York, said the United States and the European Union will renew their commitment to support voices of peace and moderation in the Muslim world.
Thousands of demonstrators are expected in Vienna to protest Mr. Bush's visit, the war in Iraq, and some tactics in the war against terrorism.
Mr. Bush will be in Vienna for less than 24 hours. He then heads to Budapest for ceremonies marking the 50th anniversary of the Hungarian Revolution.