Updated

The United States has no plans to redeploy troops or ships in response to the unrest roiling Egypt and the instability in Tunisia and Jordan, the head of the U.S. Central Command said Tuesday.

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

"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."

The U.S.-backed regime in Egypt has been badly shaken by days of anti-government protests demanding that President Hosni Mubarak step down after nearly 30 years in power, raising concerns over the stability of one of America's closest Arab allies. On Tuesday night, Mubarak told the nation he will not run for re-election during Egypt's September ballot.

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

Mattis acknowledged that several countries are currently in a state of uncertainty, and that further unrest is likely.

"We are living in a transitional period, and transitions often take longer and are less smooth than people desire — part of that may be an unrealistic demand for instant change," he said.

But he 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.

The canal is the key route to the Mediterranean and used to avoid the longer and perilous path around Africa to the Atlantic Ocean.

"When you look at the fiscal impact of that on whoever is in a position of authority in Egypt, I just can't imagine a motive to shut that down," said Mattis, who succeeded Gen. David Petraeus as head of the military's Central Command in August.

"Were it to happen, obviously we would have to deal with it diplomatically, economically, militarily — but that to me is hypothetical," he said.

Mattis, speaking at London think tank Policy Exchange, was making his first public speech in Europe since taking his post overseeing the end of U.S. combat operations in Iraq, the war in Afghanistan, and other missions in the Middle East.

He acknowledged that U.S. plans to begin withdrawing troops from Afghanistan in July could give a temporary boost to the Taliban and other insurgent groups who have claimed foreign troops are abandoning the country.

The withdrawal marks the start of a process aimed at the pullout of all NATO combat forces from Afghanistan by 2014.

"I think to some degree, in the short term, it may give them heart," Mattis said. "But, it undercuts their narrative ... especially come August when they see we're still there."

He said the international mission in Afghanistan was showing signs of "inexorable progress" but said that military successes were not yet irreversible.