The support ship, General Frank S Besson, set sail from a military base in the state of Virginia on Saturday.

It comes after President Joe Biden said the US would build the floating harbour to help get aid into Gaza by sea.

The UN has warned that famine in the Gaza Strip is "almost inevitable" and children are starving to death.

The US and Jordan carried out an airdrop on Sunday, parachuting in more than 11,500 meals that included rice, flour, pasta, and canned food, the US military said.

Aid deliveries by land and air have proved difficult and dangerous.

The World Food Programme had to pause land deliveries after its convoys came under gunfire and looting. And on Friday, there were reports that five people had been killed by a falling aid package, when its parachute failed to open properly.

The US ship departed "less than 36 hours" after Mr Biden made his announcement, US Central Command wrote on X.

It is "carrying the first equipment to establish a temporary pier to deliver vital humanitarian supplies" to Gaza, the statement continued.

The Pentagon has said it could take up to 60 days to build the pier with the help of 1,000 troops - none of whom would go ashore.

Charities have said those suffering in Gaza cannot wait that long.

Meanwhile, an aid ship laden with some 200 tonnes of food had been expected to set sail from a port in Larnaca, Cyprus on Sunday afternoon, Cypriot media reported.

However as Sunday night ticked into Monday morning, it was still docked in Cyprus.

The charity World Central Kitchen (WCK), which has provided the food aid, told the BBC: "This maritime operation remains a quickly evolving and fluid situation... we plan to embark as soon as possible."

It follows an EU announcement that a new sea route would be opened over the weekend to allow aid to sail directly from Cyprus - the closest EU country to Gaza.

The ship, Open Arms, belongs to the Spanish charity of the same name. Exactly where it plans to dock when it reaches Gaza has not been publicly revealed.

Gaza has no functioning port and its surrounding waters are too shallow for large vessels, but WCK said its team had been building a jetty off the coast to receive the aid.

The charity added that its plans are "not related" to the floating pier the US is aiming to build.

Israel has welcomed the ocean initiative, and said aid would be delivered after security checks were carried out in Cyprus "in accordance with Israeli standards".

Israel's military launched an air and ground campaign in the Gaza Strip after Hamas's attacks on Israel on 7 October, in which about 1,200 people were killed and 253 others were taken hostage.

More than 30,900 people have been killed in Gaza since then, the territory's Hamas-run health ministry says.

The conflict has created a growing humanitarian crisis, and the UN has warned that at least 576,000 people across the Gaza Strip - one quarter of the population - are facing catastrophic levels of food insecurity.

Western countries have pressed Israel to expand land deliveries by facilitating more routes and opening additional crossings.

Lorries have been entering the south of Gaza through the Egyptian-controlled Rafah crossing and the Israeli-controlled Kerem Shalom crossing. But the north, which was the focus of the first phase of the Israeli ground offensive, has been largely cut off from assistance in recent months.

An estimated 300,000 Palestinians are living there with little food or clean water.

Israel has been accused of hampering aid efforts, and an independent UN expert last week accused it of mounting "a starvation campaign against the Palestinian people in Gaza".

Yeela Cytrin, a legal adviser at the Israeli mission to the UN, responded that "Israel utterly rejects allegations that it is using starvation as a tool of war", before walking out in protest.

By Tiffany Wertheimer