The United Nations said that although aid trucks began to cross the border after an 11-week lockdown, no aid has been distributed in Gaza.
Israeli officials said 93 trucks entered Gaza on Tuesday, carrying aid, including flour, baby food, medical equipment and medicines.
But the UN said that despite the trucks reaching the Palestinian side of Kerem Shalom Crossing, no aid has been allocated so far.
Its spokesman Stephane Dujarric said a team “waited for hours” so that Israel could allow them to enter the area, but “unfortunately, they were unable to bring the supplies into our warehouse.”
Israel agreed on Sunday to allow “essential food” to enter Gaza, with global experts warning of the looming famine.
But international pressure on Israel continues to grow.
Britain said it would suspend trade negotiations on Israel's "morally unreasonable" military escalation in Gaza, while Prime Minister Sir Kyle Stamer described the situation as "unbearable".
Meanwhile, EU Foreign Policy Director Kaja Kallas said the group will review trade agreements with Israel based on its actions in Gaza.
Dujarric said the aid operation was “complexed” as Israel asked the UN to “unload supplies on the Palestinian side of Kerem Shalom Crossing and once they gain access to our team from inside the Gaza Strip, they would reload them separately.
He added that the arrival of supply was a positive development, but described it as “what needs is what is needed”.
The United Nations body is estimated to require 600 trucks a day to start solving the chronic humanitarian crisis in Gaza.
Earlier, UN Humanitarian Chief Tom Fletcher told the BBC that the BBC could die in Gaza if Israel does not immediately give aid.
"Unless we can reach them, we will die within the next 48 hours," Fletcher said in an interview with the BBC's Program Today.
When he was about how his arrival arrived, he said there were strong teams in the "field team" operating in the medical centers and schools - but no more details were provided.
The BBC later requested clarification of the United Nations Coordination for Humanitarian Affairs (UNOCHA) figures, the person said: "We pointed out that there are an estimated 14,000 babies with severe acute malnutrition in Gaza because the IPC partnership has been in the following circumstances as we need to be in the supply range.
It highlighted a report from the Integrated Food Security Stage Classification (IPC), which noted that between April 2025 and March 2026, there will be 14,100 severe acute malnutrition cases between 6 and 59 months.
This could happen in about a year - not 48 hours, the IPC reports.
When pressure was put on the press conference, Unocha spokesman Jens Laerke said: "Now, I just want to say that we know that some babies urgently need these supplements for life-saving supplements because their mothers can't support themselves."
"If they don't get this, they'll be in fatal danger," he said.
Last week, Hamas-operated Health Department reported that malnutrition children died of malnutrition in the past 11 weeks.
U.S. Secretary of State Marco Rubio welcomed Israel’s decision to allow Gaza aid and told the Senate Foreign Relations Committee: “We are pleased to see aid starts flowing in again.”
Rubio said responding to a Democrat saying that the number of aid trucks allowed was too small: “I understand that your point of view is not enough, but we’re happy to see the decision being made.”
On Monday, leaders from the UK, France and Canada issued a statement calling on the Israeli government to “stop its military operations” and “immediately allow humanitarian aid to enter Gaza.”
As part of today’s announcement, the UK has also imposed sanctions on several prominent Israeli settlers and settlers linked groups.
Israel launched a military campaign in Gaza on October 7, 2023 in response to Hamas' cross-border attacks, in which about 1,200 people were killed and another 251 were taken hostage.
According to the region's health ministry, at least 53,475 people have killed 3,340 people in Gaza since then, including 3,340.