A human rights organisation has called on Cambodia to stop interfering in preparations for the trials of former leaders of the Khmer Rouge.
Khmer Rouge victims have already had to wait 30 years for justice
Human Rights Watch blamed government interference for the recent failure by Cambodian and foreign judges to agree on rules for the UN-backed tribunal.
Cambodia dismissed the accusation as "politically motivated".
About two million people died during the years that the Khmer Rouge ruled Cambodia in the 1970s under Pol Pot.
The trials are due to start next year and aim to put the surviving leaders of the brutal Maoist regime - some of whom are still living freely - in the dock.
A week-long meeting between Cambodian and international legal officials last month broke up following "substantive disagreement" over the rules that would govern the tribunal.
HRW said Cambodian officials had acted on instructions from government officials by delaying the adoption of draft rules.
"Many of the Khmer Rouge leaders are old and increasingly frail, but until the rules are adopted, prosecutions and trials cannot move forward," said Brad Adams, Asia director of HRW.
"Political interference has brought the whole process to a screeching halt."
But government spokesman Khieu Kanharith adamantly rejected the accusations, calling them politically motivated and saying tribunal officials were just being thorough about working through complex legal issues.
Up to two million people were murdered, starved or worked to death between 1975 and 1979 under the Khmer Rouge regime.
Pol Pot, the founder and leader of the Khmer Rouge, died in a camp along the border with Thailand in 1998.
Other key figures have also died. Ta Mok - the regime's military commander and one of Pol Pot's most ruthless henchmen - died on 21 July 2006.