WASHINGTON (Reuters) - The U.S. military has started constructing a maritime pier that will allow humanitarian aid into Gaza, the Pentagon said on Friday, a move that had been expected, with the jetty set to become operational by early May.

In March, President Joe Biden announced that the military would build a temporary port on Gaza's Mediterranean coast to receive humanitarian aid by sea.

The construction is part of an effort to avert famine in the Palestinian enclave five months into Israel's military campaign against Hamas, which has devastated the tiny Gaza Strip and plunged its 2.3 million people into a humanitarian catastrophe.

"I can confirm that U.S. military vessels, to include the USNS Benavidez, have begun to construct the initial stages of the temporary pier and causeway at sea," Pentagon spokesperson Major General Patrick Ryder told reporters.

The U.N. has warned Gaza faces famine and has complained of "overwhelming obstacles" in getting in aid and distributing it around the enclave.

Aid agencies and the Biden administration have implored Israel to ease access for relief supplies into Gaza and to give their convoys safe passage inside the territory.

Ryder said the Pentagon was tracking some type of mortar attack in Gaza that caused minimal damage in the marshalling area for the pier. But he added that U.S. forces had not started moving anything to that area yet and there were no U.S. forces on the ground.

(Reporting by Idrees Ali and Phil Stewart, Editing by Rosalba O'Brien)