RIYADH, Saudi Arabia – Plunging into his maiden mission to the Middle East, President Barack Obama was greeted in this desert kingdom Wednesday by a Royal Honor Guard with 21-gun salute — and the release of a threatening audio tape by Osama bin Laden.

Aides say Obama's big message will be that he wants to build a bridge to the Arab and Muslim worlds so the U.S. can move forward in its relationships. But at the same time, he will raise tough issues like democracy, human rights and the challenges of negotiating Middle East peace.