Miroslav Jenca, United Nations assistant secretary-general for Europe, Central Asia, and the Americas, warned during a Security Council meeting that the announced plans of Israel taking control of the entire Gaza Strip would have "catastrophic consequences". The top UN official said that it could "further endanger the lives of the remaining hostages in Gaza" and be catastrophic for millions of Palestinians.
Jenca added that Gaza "is and must remain an integral part of a future Palestinian state". So far, according to Israel, they control 75% of Gaza. The zones that aren't have over two million Palestinians living. According to the UN, 87% of the surface of the Strip is in militarised zones or under evacuation orders (via BBC).
Some have suggested that the threat of a total occupation is a tactic to pressure Hamas after the breakdown of ceasefire talks. However, big parts of the Israel population are against the war, as well as some military leaders.
The UN official also denounced the restriction of humanitarian assistance, and that "the aid that is permitted to enter is grossly inadequate". It's been estimated that, from the 60,000 people murdered in Palestinian, more than 1,200 were killed since the end of May when trying to access food and supplies.