Cambodian and international judges have begun talks to prevent the possible collapse of the Khmer Rouge trials.
The trials - which aim to put the surviving leaders of the brutal Maoist regime in the dock - have ground to a halt over procedural differences.
Foreign judges want full international legal standards, while the Cambodians say local law must take precedence.
About two million people died during the years that the Khmer Rouge ruled Cambodia in the 1970s.
Trial hearings are theoretically due to start later this year.
But according to the BBC correspondent in Phnom Penh, Guy De Launey, there is a real possibility that the trials will collapse before they have even started.
The international judges have made it clear that they see this week's meeting as the final chance to make sure the trials meet international standards.
"All the judges are mindful that the upcoming... meeting is of vital importance," tribunal officials said in a recent statement.
If an agreement cannot be achieved, the foreign contingent will ask the UN to pull out.
Key leaders such as Ta Mok died before reaching court
But local officials have been equally adamant that Cambodian law has to have prime importance in the special courts, and according to our correspondent, they feel they have been unfairly portrayed as being the sole cause of the delays.
There are more than 100 items under discussion at this week's talks, but many have already been resolved after lengthy informal negotiations.
Those involved admit that time is of the essence, if they are to bring elderly Khmer Rouge members to court.
"There is one point on which the international judges are unanimous - these trials should take place quickly or not at all," French judge Marcel Lemonde of France told AFP news agency.
The death of military commander Ta Mok late last year heightened fears that more key defendants and witnesses could die before facing justice.
Pol Pot, the founder and leader of the Khmer Rouge, has already died, in a camp along the border with Thailand in 1998.