Boris Johnson will join Amal Clooney at a high-level event at the United Nations on Monday to launch a British-led campaign to bring Islamic State (IS) to justice.
The Foreign Secretary and human rights lawyer will help introduce an initiative to begin gathering evidence about the terror group's "abhorrent crimes" so its members can be held to account internationally.
At the UN General Assembly in New York, they will urge world governments, NGOs and other organisations to join the campaign for justice for the victims of IS, also known as Daesh.
Ahead of the event, Mr Johnson said: "We have united to defeat Daesh, now we must unite to bring them to justice. That needs to include looking at ways for the UN to support the vital task of gathering evidence about their abhorrent crimes.
"The global campaign will seek justice for all Daesh's victims, bringing the international community together in defiance of Daesh's efforts to stoke division and hate."
The pair will be joined by the Iraqi foreign minister, the Belgian foreign minister, the UN High Commissioner for Human Rights, and IS survivor and human rights activist Nadia Murad Basee Taha.
The RAF has now conducted 1,010 air strikes - 947 in Iraq and 63 in Syria - against IS, who have used their territory in the Middle East to inspire terror attacks in Europe and across the world.