Even without firing a shot, a relatively passive operation using signal-jamming aircraft operating in international airspace could muddle Libyan government communications with military units. Administration officials said Sunday that preparations for such an operation were under way.

The latest military force to draw within striking distance of the Libyan capital, Tripoli, is the 26th Marine Expeditionary Unit aboard two amphibious assault ships, the Kearsarge and the Ponce. The unit provides a complete air, sea and land force that can project its power quickly and across hundreds of miles, either from flat-decked ships in the Mediterranean Sea or onto a small beachhead on land.

In this task force are Harrier jump-jet warplanes, which not only can bomb, strafe and engage in dogfights, but can also carry surveillance pods for monitoring military action on the ground in Libya; attack helicopters; transport aircraft — both cargo helicopters and the fast, long-range Osprey, whose rotors let it lift straight up, then tilt forward like propellers to ferry Marines, doctors, refugees or supplies across the desert — landing craft that can cross the surf anywhere along Libya’s long coastline; and about 400 ground combat troops of the 1st Battalion, 2nd Marines.