Iran helps solve the mystery.

Bush started his trip Monday in Slovenia where he will take part in the annual US-European Union summit. He also is staying in Italy to see his old friend, Premier Silvio Berlusconi, and for his third meeting with Pope Benedict XVI, visiting Germany to chat with Chancellor Angela Merkel, spending two days in Paris with French President Nicolas Sarkozy, going to Windsor Castle to see Britain's Queen Elizabeth II, and stopping in Belfast, Northern Ireland, to hail the power-sharing agreement between Protestants and Catholics .

But mostly, Bush is visiting nations and leaders critical to a stepped-up US effort to get new and harsher measures aimed at preventing Iran from proceeding with a suspected plan to build a nuclear bomb. Britain, Germany and France, along with the United States, Russia and China, are developing a package of fresh penalties and incentives aimed at reigning in Tehran's alleged atomic ambitions. Italy wants to join the effort, too, and Bush told a television interview that he was open to it.   

US President George W. Bush waves during his arrival to Ljubljana airport on June 9, 2008. Bush arrived in Slovenia on Monday for his farewell US-European Union summit at the start of a week-long tour of the continent. [Agencies]

 "He is going to try to stiffen European resolve on Iran," said Stephen J. Flanagan, director of the international securities program at the Center for Strategic and International Studies. "If anything else is going to happen ... those are the countries that are going to deliver."