United Nations Secretary-General Ban Ki-moon, right , accompanied by Cambodia's Prime Minister Hun Sen, inspects the guard of honour at the parliament house in Phnom Penh.

Phnom Penh - Cambodia will not allow the UN-backed Khmer Rouge tribunal to prosecute former low-ranking officers of the genocidal regime because it would endanger national peace, the country's leader told the UN chief on Wednesday.

Prime Minister Hun Sen's comments, made during a two-hour meeting with UN Secretary-General Ban Ki-moon, were the government's latest obstruction of UN efforts to bring more Khmer Rouge leaders to justice.

Ban was visiting Cambodia as part of a four-country Asian tour.

The UN-assisted tribunal, which has a history of contentious relations with the Cambodian government, was a focus of Ban's trip to Cambodia. After meeting the prime minister, Ban headed to the tribunal to hold a town hall-style meeting with its staff.

The 1975-79 Khmer Rouge regime was blamed for the deaths of some 1,7 million people from starvation, disease, overwork and execution.

After 30 years and lengthy delays, the tribunal's first conviction came in July when the Khmer Rouge's chief jailer was sentenced to 19 years in prison, closing what was known as Case 001. Kaing Guek Eav, also known as Duch, was convicted of war crimes and crimes against humanity.

Case 002 is expected to start next year against the four top surviving Khmer Rouge leaders, who are accused of war crimes, genocide and crimes against humanity.

International co-prosecutors at the tribunal have tried to launch a new case - 003 - against lower-ranking officers accused of murder, torture and other crimes. But they say progress has been blocked by political interference from Cambodian officials who oppose more prosecutions.

“Hun Sen has said clearly that there will be no case 003 allowed. We have to think about peace in Cambodia,” Foreign Minister Hor Namhong told reporters after the meeting with Ban.

Hun Sen has repeatedly said that bringing more Cambodians to trial could harm national peace and healing and that the nation needs to move on.

Critics accuse Hun Sen of trying to limit the tribunal's scope to prevent his political allies from being indicted. Hun Sen once served as a Khmer Rouge officer and many of his main allies are also former members of the group.

Ban started his Asia tour in Thailand and will also visit Vietnam and China. - Sapa-AP