On a visit to London, Gen. James Mattis said military leaders and lawmakers were closely watching developments, but that he had no orders to rearrange his forces in response.

The U.S.-backed regime in Egypt has been badly shaken by days of increasingly confident calls for President Hosni Mubarak to step down after nearly 30 years in power, raising concerns over the stability of one of America's closest Arab allies.

Protests across Egypt follow the ouster last month of Tunisia's president and the decision by Jordanian King Abdullah II to sack his country's government.

"These issues do not call for a military solution right now," Mattis said. "There's no reason right now for any shift in military forces, or anything like that. I've not received any orders."

Mattis also said it was unlikely events in Egypt would lead to difficulties for ships passing through the Suez Canal — another major concern for lawmakers and businesses.