Some 200 additional U.S. military personnel will be moving ashore in Liberia soon. Not all will remain on the ground overnight but it is the biggest American force committed so far to the West African-led peacekeeping effort in the war-torn country.
The bulk of the new U.S. force will be some 150 Marines who will temporarily act as a land-based quick reaction unit.
Senior Pentagon officials stress the deployment is not intended to meet any specific threat.
Instead Lieutenant General Norton Schwartz of the Pentagon's Joint Staff says the Marines will only be used if West African peacekeepers, known as the ECOMIL force, run into unexpected trouble, especially as they move into the port of Monrovia, Liberia's capital.
"It is a reaction capability if something unexpected occurs to an ECOMIL unit and only again to stabilize the tactical situation such that they can restart their mission," he said. "It is not a security mission."
In addition, General Schwartz tells reporters aircraft aboard the amphibious assault ship Iwo Jima off Monrovia will be made available to act as airborne escorts when West African troops make the port move.
Besides the quick reaction force, other U.S. personnel the Pentagon is sending in will include Navy Seals who will ensure the waterway leading into the port is free of any obstacles. Military engineers will conduct an overall port assessment to ensure shiploads of humanitarian aid can enter.
Some 2,300 Marines are aboard the three-ship Iwo Jima group off the coast of Liberia.
But until now, fewer than 100 American military personnel have been in Monrovia. Most are security forces at the U.S. embassy compound with a small liaison unit working with West African peacekeeping troops.
Pentagon officials say the quick reaction force is expected to move back offshore to the Iwo Jima group when additional West African peacekeepers arrive in Liberia, perhaps by the end of this week.
In the meantime, defense officials are ruling out any move by any of the ships in the Iwo Jima group into Monrovia's port.
Instead they say top priority will be given to bringing into the port a World Food Program vessel carrying aid that is now laying offshore. Pentagon officials say it is loaded with both food and fuel.
Thousands of hungry Liberians stormed the rebel-held port Wednesday, looting warehouses containing humanitarian supplies.
Rebel fighters guarding the warehouses initially fired shots in the air to stop the chaos. They eventually gave up and let people take as much as they could.
The rebels have agreed to surrender the port to West African peacekeepers on Thursday.
Monrovia has been calm since ousted leader Charles Taylor resigned and left Liberia on Monday for exile in Nigeria.