The tribunal has secured three convictions since it opened in 2006. They produced life sentences for Kaing Guek Eav, or Duch, the brutal head of an interrogation center, and for the two current defendants, Mr. Nuon Chea and Mr. Khieu Samphan, who were found guilty in an earlier trial of crimes against humanity. Mr. Nuon Chea and Mr. Khieu Samphan were being tried on a different set of charges this time.

Mr. Nuon Chea and Mr. Khieu Samphan are the last survivors of a tightknit group that tried to turn Cambodia into an agrarian utopia, killing off its educated people and reorganizing the country into what amounted to a nationwide labor camp.

Pol Pot died in 1998, and two of the original defendants in this trial have died since it began.

The three lower-ranking cadres are Meas Muth, a former naval commander; Ao An, a former deputy secretary for the Central Zone; and Yim Tith, a former acting secretary of the Northwest Zone. They are accused of genocide and crimes against humanity.

Citing questions about funding, two investigating judges have said that they are prepared to issue a stay of proceedings against the three men, effectively putting an end to the tribunal once the two current cases are completed.

The judges said a decision on the disposition of the cases could come as early as next Friday.

The trial is a combined enterprise of the United Nations and the Cambodian courts. Most of its funding comes from international donor nations whose generosity has been strained as the trial has dragged on and other priorities have taken its place.