Cambodian Prime Minister Hun Sen warned on Tuesday that putting more Khmer Rouge cadres on trial for crimes committed during Pol Pot's 1975-79 reign of terror could plunge the country back into civil war.
"I would prefer to see this tribunal fail instead of seeing war return to my country," Hun Sen, himself a former Khmer Rouge commander, said a day after the joint UN-Cambodian court resumed its trial of Pol Pot's chief torturer.
Duch, former head of the S-21 prison where more than 14,000 "enemies" of the ultra-Maoist revolution died, is the first of five ageing senior cadres to face trial 30 years after the end of a regime blamed for 1.7 million deaths in Cambodia.
Human rights groups have used this week's trial to push for investigations of more suspects, arguing that would ensure justice is delivered to millions of victims and survivors.
But Hun Sen, speaking at the opening of an industrial zone in the port of Sihanoukville, said the trials should not go beyond the five charged with war crimes and crimes against humanity.
"If as many as 20 Khmer Rouge are indicted to stand trial and war returns to Cambodia, who will be responsible for that?" he told the audience.
After Duch, the others awaiting trial are "Brother Number Two" Nuon Chea, the regime's ex-president Khieu Samphan and Ieng Sary, its foreign minister, and his wife.
They have denied any wrongdoing. Duch has expressed remorse for his victims, but said he was following orders.
The court admitted in January that a bid to go after more suspects was brushed aside by the Cambodian co-prosecutor, who argued it would not be good for national reconciliation.
A final ruling on the additional cases - details of which the court has not disclosed but the number of which has been put at six in media reports - is still pending.
"The issue regarding the jurisdiction of the court and whether or not to have further suspects is complicated," said Helen Jarvis, an Australian working for the tribunal.
The government has denied meddling in the court, but rights activists have long suspected Hun Sen does not want it to dig too deep for fear it will unearth secrets about senior Khmer Rouge figures inside his administration.
Hun Sen, 58, joined the Khmer Rouge during their 1970-75 guerilla war against the US-backed government of General Lon Nol. He rose to be a junior commander and lost an eye in fighting just before the rebels took the capital, Phnom Penh.
He has said he defected to Vietnam in mid-1977 and played no part in Pol Pot's bloody agrarian revolution, in which an estimated 1.7 million people, or a third of the population, died.
Vietnamese troops invaded in late 1978 and installed a communist government made up mostly of former Khmer Rouge cadres including Hun Sen, who became premier in 1985.
Analysts said Hun Sen's opposition to expanding the tribunal's work may reflect his concerns former Khmer Rouge commanders will flee back to the jungle and fight any move to arrest them.
Pol Pot's death in 1998 was followed by a formal Khmer Rouge surrender that helped usher in a decade of peace and stability, threatened now by the global economic downturn.