"We are very concerned about the possible risk of disruption to the judicial process through the strike by national staff," Olsen said in an email Monday. "The U.N. is also concerned for the welfare of the national staff and their families."
The tribunal has met with resistance from the Cambodian government, where many top officials are former Khmer Rouge members. The Cambodian government is officially responsible for paying the salaries of the court's Cambodian employees, but has often failed to supply adequate funds, leaving international donors to pick up the slack.
"We call on the Royal Government immediately to meet its obligation to pay the national salaries so that the strike can be averted," Olsen said. "The U.N. is also working closely with the principal international donors to explore all possibilities for averting the crisis."
The Cambodian-run section of the court currently faces a $3 million shortfall for its operations, including wages, from June through the end of the year, Neth Pheaktra said.
He said the strike meant there was a "high risk" that the closing arguments for the current section of the trial, scheduled for mid-October, would be delayed.
The tribunal is currently trying two former Khmer Rouge leaders, former head of state Khieu Samphan, 82, and chief ideologue Nuon Chea, 87, for crimes against humanity, war crimes, genocide and other offenses. Leng Sary, another defendant, died in March during the trial.