US defence secretary Robert Gates arrived on Friday in Jordan on a previously unannounced visit for talks with key ally King Abdullah II, as anti-regime protesters rallied in Amman.
Gates is calling on Arab leaders to move quickly to adopt major reforms in the face of popular anger.
US officials say the king has been more active in pursuing reforms compared to other leaders in the region.
And as western aircraft kept up bombing raids over Libya, Gates is expected to give the king an update on coalition operation against Muammar Gaddafi's regime.
Washington is concerned about the effect of the unrest on their allies, like Jordan, where people have held protests since January, calling for far-reaching political reforms and an end to what they say is rampant corruption.
The US defence chief was in Israel, pressing Israeli and Palestinian leaders to take "bold action" for peace despite soaring tensions, saying political upheaval in the region offered an opportunity.