More than 200 trucks carrying roughly 3,000 tons of aid had been positioned near the crossing for days before it was allowed through.

US embassy officials said they had received information the crossing would open on Saturday - but are unsure how long it will remain so to allow foreign nationals to leave Gaza, which has been bombarded by airstrikes.

Foreign Secretary James Cleverly tweeted on Saturday morning: "Trucks carrying lifesaving aid are beginning to cross at Rafah into Gaza. This aid is a lifeline for those suffering. But it cannot be a one off.

"The UK continues to push for humanitarian access to Gaza."

Read more: Israel-Gaza latest updates

The US embassy said in a statement on Saturday morning: "We anticipate that many people would attempt to cross should the border open, and US citizens attempting to enter Egypt should expect a potentially chaotic and disorderly environment on both sides of the crossing."

The situation remains "dynamic and fluid" and the security environment is "unpredictable", the embassy warned.

"You should assess your personal safety and security before choosing to move towards the border or trying to cross."

The border - Gaza's only gateway to the rest of the world that is not directly controlled by Israel - has been closed since the deadly Hamas attack on 7 October.

It had been due to open on Friday under an agreement brokered by US President Joe Biden, but the White House last night said the "modalities" of the gate being opened were still under discussion.

UN Secretary General, António Guterres, begged for life-saving aid to be allowed to pass through the crossing into Gaza.

Speaking from the Egypt side of the border on Friday, he said "On this side, we have seen so many trucks, loaded with water, with fuel, with medicines, with food.

"Exactly the same things that are needed on this (Gaza) side of the wall.

"So these trucks are not just trucks, they are a lifeline.

"They are the difference between life and death for so many people in Gaza," he said - urging that "as many trucks as possible should be moved as quickly as possible".

Two hostages freed - as Israel vows to 'fight until victory'

An imminent announcement about the status of the Rafah crossing comes as two US citizens held captive by Hamas were freed.

The militant organisation released footage of the mother and daughter Judith and Natalie Raanan walking to freedom, with Natalie's father, Uri Raanan, saying she is "doing very good".

They are among 203 hostages captured by Hamas fighters and brought back to Gaza.

Israeli Prime Minister, Benjamin Netanyahu, vowed Israel would "continue to fight until victory" after confirming the release of the hostages on Friday night.

"Two of our abductees are at home. We are not giving up on the effort to return all abducted and missing people," he said.

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