WASHINGTON (CNN) — The fighting that erupted in Lebanon has prompted the Pentagon to develop scenarios for evacuating American citizens, estimated to number around 25,000, military sources told CNN.

The rapid widening of the Mideast conflict this week has created great concern in the U.S. government, which doesn’t want Americans in Lebanon caught in the middle of a shooting war.

Such moves would start small, if they happen at all, the sources said. There has been no immediate request for help and no order to move any military personnel.

The State Department has set up a Middle East Task Force to coordinate policy and share information. Defense Department officials are part of the team to talk about any possible plans for American evacuation — a customary move, said State Department spokesman Sean McCormack.

While "contingency planning" is being done, no evacuations were under way, McCormack told reporters. Americans were being asked to stay in contact with the American Embassy.

Americans in Lebanon can call the following numbers for information: 1-202-501-4444 from overseas, or 1-888-407-4747 in the United States. U.S. citizens can register with the embassy online at https://travelregistration.state.gov/ibrs/.

The developing of scenarios has been complicated by the fact that Israel bombed the Beirut International Airport during its operations in Lebanon.

The airport would have been the logical place for Americans to depart Lebanon.

Sources said that in one scenario, the Pentagon would find another air field and work with the Lebanese government on an agreement where U.S. aircraft could come in and evacuate a relatively small number of U.S. Embassy workers.

A second option would be moving a Marine amphibious unit led by the USS Iwo Jima into the area, with the carrier and unit remaining offshore.

The group is currently in the Red Sea on exercises with Jordan, but could be moved into the Mediterranean Sea off the Lebanese coast.

Such a scenario — which would take some time to pull off — would be used only if the a large evacuation operation was needed, and it would come only at the ambassador’s request, the sources said.