But critics say its integrity is threatened by allegations of corruption and political interference over whom to prosecute.
"Any hint of political manipulation at the tribunal will undermine its credibility with the Cambodian people," said Sara Colm, Cambodian-based senior researcher at Human Rights Watch.
Four other Khmer Rouge cadres have been charged but a bid to go after more suspects was brushed aside last month by the tribunal's Cambodian co-prosecutor, who said it would not help national reconciliation.
Cabinet spokesman Siphan Phay denied any meddling and said the government wanted to complete the trials of the five people already facing charges before going after other suspects. "First things first," he told reporters. "We have never said we opposed anything, but let's finish these first."
Reuters contributed to the reporting of this story.