Oscar-winning actor George Clooney has made an impassioned speech to the UN Security Council over continuing violence in the Darfur region of Sudan.
George Clooney has been a regular campaigner on Darfur
He told council members genocide was taking place "on your watch", and how they responded would be their legacy.
Mr Clooney was speaking at a special informal session hosted by the US ambassador to the UN, John Bolton.
Sudan has rejected a UN resolution authorising a 20,000-strong force for Darfur as an attack on its sovereignty.
But the UN says violence and displacement have increased in Darfur, despite a May peace deal.
Some 200,000 people have been killed and more than two million driven from their homes in three years of fighting.
'Voice of the victims'
Mr Clooney and his journalist father, Nick, spent five days in Darfur in April hearing personal stories of some of the victims of the fighting, and have campaigned on it since.
"I'm here to represent the voices of the people who cannot speak for themselves," Mr Clooney told Security Council members.
Opponents denounce the proposed UN force as "colonial"
"We know how difficult a task this is... but you are the UN and this is the task that you have been given...
"It is the first genocide of the 21st Century and if it continues unchecked, it will not be the last."
Mr Clooney said if the UN force did not go in on 1 October - when the mandate of the current, under-resourced African Union force ends - "aid workers will have to leave and if they leave that leaves a couple of million people with absolutely nothing".
"How you deal with it is your legacy," he said.
"It's your Rwanda - your Cambodia - your Auschwitz. We are one 'yes' away from ending it."
But diplomats have baulked at the suggestion the UN should "shoot its way in" to Darfur without the consent of Sudan.
Nobel laureate and Holocaust survivor Elie Wiesel, whose Foundation for Humanity organised the session, also addressed the council.
"You are the last political recourse of Darfur victims and you can stop it," he said.