Updated

A United Nations-assisted tribunal on Wednesday cleared the way to begin the genocide trial of two elderly former top leaders of Cambodia's 1970s Khmer Rouge regime.

Survivors of the communist regime's reign of terror, along with students and Buddhist monks, attended a hearing that laid down the ground rules for the trial, which judges said would likely start in September or October.

The defendants, Khieu Samphan, 83, and Nuon Chea, 88, were in the top leadership of the 1975-79 regime, which is generally held responsible for the deaths of about 1.7 million people from starvation, exhaustion, disease and execution.

The two are scheduled to hear the verdict next week of a first trial against them for war crimes and crimes against humanity, related mostly to the forced movement of millions of people to the countryside when the Khmer Rouge took power.

At Wednesday's hearing, the chief judge, Nil Nonn, read out the new charges before lawyers began debating witness lists, reparations requests and procedural objections.

Khieu Samphan attended the hearing and appeared to be in good health, at times taking notes. Nuon Chea, however, remained in his holding cell because he is unable to sit for long periods of time.

Because of the advanced age and poor health of the defendants, the case against them has been divided into separate trials, in hopes that they will live long enough to have some judgments against them completed.

Legal experts and lawyers have argued that such an approach muddies the pursuit of justice.

Anta Guisse, a lawyer for Khieu Samphan, said she was concerned her client would not get a fair trial amid confusion over what evidence or findings from the first trial would be carried over into the upcoming one.

Among the scores of proposed witnesses, lawyers for Nuon Chea urged the court to consider calling three senior members of Cambodia's current government: National Assembly President Heng Samrin, Senate President Chea Sim and Sen. Ouk Bunchoeun.

All three served as high-ranking cadres before defecting from the Khmer Rouge and aiding in its overthrow. Long-serving current Prime Minister Hun Sen also was a Khmer Rouge defector.

Previous efforts by the defense to have members of the government testify have stoked political tensions and been shot down.

The first trial began in November 2011 with four defendants, but Khmer Rouge Foreign Minister Ieng Sary died in March 2013, and his wife, Social Affairs Minister Ieng Thirith, was deemed unfit to stand trial due to dementia.

Nuon Chea and Khieu Samphan required occasional hospitalization, slowing the proceedings.

Although Wednesday's hearing was purely procedural, it stirred unpleasant feelings for some.

Om Bopha, 59, a Khmer Rouge survivor who was a victim of forced marriage, said she attended the hearing hoping to see the judicial process in action. Instead, she said, "Once I arrived in the court and saw Khieu Samphan's face, it made me think me that the Khmer Rouge have not yet been toppled."

"It seemed like I am still living under their regime," Om Bopha said, choking back tears.

Mil Poch, 55, who lost five siblings during those dark years, also attended. "I wanted the court to convict and sentence the two defendants to life in prison because they have killed so many people," he said.