Cambodian translators angry that they have gone without pay for three months stopped working at the U.N.-backed genocide trial of former Khmer Rogue leaders on Monday, a new setback for an international justice effort that has been hobbled by conflicts with the Cambodian government.

Khmer Rouge tribunal spokesman Neth Pheaktra said that about 30 Cambodian staff members from the translation section announced they were going on strike just before the court was to hear testimony from a foreign expert. Testimony that had been scheduled to be given this week and next has been postponed until the dispute can be resolved, he said.

Neth Pheaktra said local staff members who worked at the tribunal have not been paid since December because the countries that have agreed to fund the tribunal have not contributed on time. Foreign workers involved in the trial are paid through a separate budget.

The court has appealed to donors for more money, Neth Pheaktra said, but he added that it was unclear when the workers might be paid.

The tribunal, which formed in 2006, is tasked with seeking justice for atrocities committed by the Khmer Rouge during its four years in power in the late 1970s. An estimated 1.7 million Cambodians died under the radically communist regime from forced labor, starvation, medical neglect and execution.

Three former leaders have been on trial since November 2011, charged with crimes against humanity, war crimes, genocide and other offenses: Khieu Samphan, the 81-year-old former head of state, Nuon Chea, the 86-year-old chief ideologist of the group, and Ieng Sary, 87, the former foreign minister. A fourth defendant, former social affairs minister Ieng Thirith, was deemed mentally unfit and set free.

The defendants' age and infirm health has raised concerns they may not live long enough to hear a verdict. Just one person, chief Khmer Rouge jailer Kaing Guek Eav, has been convicted by the tribunal so far; he is serving a life sentence.

Tribunal officials have sought to prosecute other former Khmer Rouge leaders, but Hun Sen, who has ruled Cambodia since 1985, has warned that more trials will "not be allowed." Many people in Cambodia's government, including Hun Sen himself, are former Khmer Rouge officials. Frustration over government pressure prompted Swiss judge Laurent Kasper-Ansermet to resign from the tribunal last year.

Neth Pheaktra said translators are essential to the proceedings, which used three languages: English, French and Cambodian. About $9.3 million is needed for salaries and daily operating costs in 2013 for the Cambodian component of the operation, he said.

The tribunal, which spent $141.1 million from 2006 through 2011, has warned that it faces severe budgetary shortfalls.

Neth Pheaktra said the budgets for international staffers are adequate at the moment but will last only until the middle of this year. Japan is the biggest contributors to the tribunal with nearly $80 million in total, while France, Germany and Britain are also major donors.