Cambodia's prime minister has said a tribunal to try former Khmer Rouge leaders is at risk unless Phnom Penh gets help with its share of the cost.
Khmer Rouge victims have already had to wait 30 years for justice
Hun Sen said Cambodia was $11.8m short of the funds it agreed to contribute.
"It has been quite a headache for me. Sometimes, I have even thought of letting it [the tribunal] slide," he said on Monday.
The tribunal, which is expected to run for three years, is mainly being funded by the UN.
Hun Sen now wants the international community to pledge more than its $43m share.
"If they don't give money, no trial will be convened," he said.
Cambodia, one of Asia's poorest countries, has said it can only contribute $1.5m - well short of the $13m it was expected to give.
The UN announced in April that it had raised enough money on its side for the tribunal to go ahead.
The communist Khmer Rouge regime, which ruled from 1975-79, is blamed for the deaths of more than one million people out of an eight million-strong population.
Cambodia first sought UN funding for the court eight years ago.
There are concerns that the ageing top figures of the murderous regime, who have never been prosecuted, might die before being taken to court.
The regime, headed by Pol Pot, persecuted its political opponents as well as minority groups.
They allowed food shortages to kill people by starvation, while others were forced to move from the cities to the countryside, where they died from overwork in labour camps.