Updated

The Egyptian military is protecting the U.S. Embassy as protesters continue to take to the streets in opposition of President Hosni Mubarak, a senior U.S. defense official told Fox News.

The official said the U.S. Embassy so far has not made a request for an evacuation, though the United States has evacuations plans at the ready for its embassies around the world.

"This is an issue for the Egyptian government and Egyptian security forces, but we are clearly concerned," the official said. "We are clearly watching developments."

The Egyptian Army moved in to protect the U.S. site almost immediately, the official said.

A full evacuation would be a daunting task in the middle of such turmoil. There are 50,000 Americans estimated to be in Egypt, but the official said a full evacuation could cover as many as 85,000 people, some of whom are third-party nationals which the United States is "responsible for."

Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, was at the Pentagon early Saturday morning for a 30-minute briefing from senior staff members.

The USS Kearsarge is the closest Navy vessel in the area, but it has not been ordered to move into help provide support for the evolving situation in Egypt.

Egyptian Army officers including Army Chief Lt. Gen. Sami Hafez Enan left New York last night to fly back to Egypt, according to Pentagon officials.

Fox News' Jennifer Griffin contributed to this report.