A United Nations human rights expert says she believes Israel has committed "acts of genocide" in Gaza.
Francesca Albanese will present her report on Tuesday to the UN Human Rights Council in Geneva.
But it has already been dismissed by Israel, whose ambassador described it as "an outrageous distortion of the Genocide Convention".
It comes amid growing international pressure on Israel to stop the war or to do much more to protect civilians.
Israel has for years been angered by the UN Human Rights Council's agenda, which permanently devotes an entire section - Item 7 - to scrutiny of the situation in "Palestine and the other occupied Arab territories".
The agenda item was approved not by the UN itself, but by UN member states, decades ago, and has never expired. No other country in the world has permanent scrutiny like this, and Israel views it as discriminatory, and aimed at delegitimising Israel.
But many countries, in particular those in the Middle East, argue that the situation - in the absence of self-determination for Palestinians through a two-state solution - requires ongoing investigation, and now that there is another conflict, all the more so.
Since Hamas's brutal attack on Israel on 7 October, Francesca Albanese, the UN special rapporteur on human rights in the occupied Palestinian territories, has called for the release of the hostages, and does so again in this report. In it she "firmly condemns the crimes committed by Hamas and other Palestinian armed groups in Israel on 7 October".
But she has also been outspoken in her criticism of Israel's conduct of the war in Gaza.
'Anatomy of a Genocide'
That's why her report has been awaited with both impatience, and trepidation.
Some UN officials will be alarmed at Ms Albanese's choice of a title for it: Anatomy of a Genocide. Many member states, especially those traditionally supportive of Israel, will be uncomfortable.
But UN special rapporteurs, while tasked by the UN to examine and advise on specific situations, are independent of it.
Genocide is a specific legal term, and Ms Albanese's report suggests some of the legal criteria have been fulfilled.
She cites what she says appears to be Israel's intention to destroy Palestinians as a group "in whole or in part", a key clause in the Convention against Genocide.
She mentions in particular three elements which point to possible genocide:
Killing members of the group
Causing serious bodily or mental harm to members of the group
Deliberately inflicting on the group conditions of life calculated to bring about its physical destruction in whole or in part
The death toll in Gaza, currently well over 32,000 according to Gaza's Hamas-run health ministry, the bombing of densely populated areas, and the restrictions on aid supplies (which, the UN says, have brought Gaza to the brink of famine), are all proof, the report claims, of intent to destroy the group.
Israel anger
Not surprisingly, Israeli diplomats are angry. Its ambassador to the UN in Geneva, Meirav Eilon Shahar, described the report as "an obscene inversion of reality", and accused Ms Albanese of questioning Israel's right to exist.
Many Israelis, too, are likely to be shocked. In the wake of 7 October attack, and the fact that so many Israeli families are still waiting for news of loved ones taken hostage, hearing such outspoken condemnation is hard.
And the suggestion of genocide, towards a state which was founded as a direct result of Nazi Germany's genocide of Jews, will cause deep offence.
But, as this week's vote for an immediate ceasefire at the UN Security Council shows, member states are growing impatient with Israel.
Too many well-respected UN aid agencies have warned that nowhere in Gaza is safe, that families are now eating animal feed, or grass, that amputations are being performed on children without anaesthetic.
They all say Israel is restricting vital aid supplies, and governments have begun to doubt Israel's claim that the UN is to blame for the delays.
Many will not like Francesca Albanese's choice of words, but the content of her report will add to the pressure on Israel to change its conduct of this war.
