PHNOM PENH (AP) ― A U.N.-backed tribunal on Wednesday began a hearing to prepare for the genocide trial of the two senior surviving leaders of Cambodia’s Khmer Rouge, under whose rule an estimated 1.7 million people died in the late 1970s from starvation, exhaustion, disease and execution.

Khieu Samphan, the regime’s head of state, and Nuon Chea, right-hand man to the group’s late leader, Pol Pot, are already set to face sentencing next week after being tried for crimes against humanity related mostly to the communist group’s forced movement of millions to the countryside when it took power in 1975.

The tribunal’s chief judge, Nil Non, opened the hearings by reading the charges and crime sites set to be heard in the newest trial segment.

Tribunal officials say their second trial, with witnesses and the presentation of evidence, is likely to begin in the last quarter of this year.

It will cover additional crimes against humanity, and add charges of genocide for the killings of members of Cambodia’s Vietnamese and Cham ethnic minorities.