(Corrects figure of government contribution from $6.9 million to $16.9 million in 11th paragraph)
By Prak Chan Thul
PHNOM PENH, Sept 2 (Reuters) - Cambodian staff at a Khmer Rouge war crimes tribunal went on strike on Monday, an official said, as a funding crisis deepened at a court already bogged down by resignations, political interference and the frail health of its elderly defendants.
Some 250 Cambodians have not been paid since June at the U.N.-backed court, caught up in a standoff between donors and a government criticized for its lack of support for hearings into one of the darkest chapters of the 20th century.
The national component of the Extraordinary Chambers in the Courts of Cambodia (ECCC) had a shortfall of $3 million in its annual budget, said court spokesman Neth Pheaktra.
About 100 went on strike and would not return until they had been paid, he said.
Up to 2.2 million people died under the ultra-Maoist Khmer Rouge regime from 1975 to 1979, about a quarter of the population, many through hard labour, torture or execution.
Under the agreement for the tribunal, the United Nations was to pay for international staff and operations, while Cambodia paid for the national side, but the government has been repeatedly criticised for its lack of support.
"We are very concerned about the possible risk of disruption to the judicial process through the strike by national staff," said U.N. spokesman Lars Olsen.
The funding dispute puts the spotlight on the commitment of the government, which has been accused of interfering behind the scenes to undermine the court and limit the scope of investigations that could implicate powerful political figures.
The court, dogged from the outset by allegations of corruption, political interference and profligacy, had spent $175.3 million by the end of last year.
It has only convicted one prisoner, former prison chief Kaing Guek Eav, alias "Duch", who was jailed for life for the deaths of more than 14,000 people.
The government said on Monday that it had already contributed $16.9 million to the court.
"If the ECCC is going to fail just because of a budget shortfall, the failure of the court is the failure of the United Nations, the failure of the Cambodian government and the failure of the international community as the whole," government spokesman Ek Tha said.
"We hope the international community will not stand and watch." (Editing by Nick Macfie)