WASHINGTON — Trucks carrying badly needed aid for the Gaza Strip rolled across a newly built American pier and into the besieged enclave for the first time Friday.

The shipment is the first in an operation that American military officials anticipate could scale up to 150 truckloads a day, all while Israel presses in on the southern city of Rafah in its 7-month offensive against Hamas.

America and aid groups warn, though, that the floating pier project is not a substitute for land deliveries that could bring in all the food, water and fuel needed in Gaza. Before the war, more than 500 truckloads entered the territory on an average day.

The operation’s success also remains tenuous because of the risk of attacks by Hamas, logistical hurdles, and a growing shortage of fuel for the trucks. Aid agencies say they are running out of food in southern Gaza and fuel is dwindling.

Troops finished installing the floating pier on Thursday, and the American military’s Central Command said the first aid crossed into Gaza at 9 a.m. Friday. It said no American troops went ashore in the operation.

“This is an ongoing, multinational effort to deliver additional aid to Palestinian civilians in Gaza via a maritime corridor that is entirely humanitarian in nature, and will involve aid commodities donated by a number of countries and humanitarian organizations,” the command said.

The Pentagon said no backups were expected in the distribution process, which is being coordinated by the United Nations.

American officials said the initial shipment totaled as much as 500 tons of aid. America has closely coordinated with Israel on how to protect the ships and personnel working on the beach.

Pentagon officials have made it clear that security conditions will be monitored closely and could prompt a shutdown of the maritime route, even if just temporarily. 

Vice Admiral Brad Cooper, a deputy commander at the American military’s Central Command, told reporters Thursday that “we are confident in the ability of this security arrangement to protect those involved.”

Already, the site has been targeted by mortar fire during its construction, and Hamas has threatened to target any foreign forces who “occupy” the Gaza Strip.

Biden has made it clear that there will be no American forces on the ground in Gaza, so third-country contractors will drive the trucks onto the shore.

Israeli forces are in charge of security on shore, but there are also two American Navy warships nearby that can protect American troops and others.

The aid for the sea route is collected and inspected in Cyprus, then loaded onto ships and taken about 200 miles to the large floating pier off the Gaza coast. 

There, the pallets are transferred onto the trucks that then drive onto the Army boats, which will shuttle the trucks from the pier to a floating causeway anchored to the beach. Once the trucks drop off the aid, they return to the boats.