By Guy de Launey BBC News, Phnom Penh

Khmer Rouge victims have already had to wait 30 years for justice

A pledging conference is scheduled to start on Monday in New York. Funding is the final obstacle to the tribunal after years of delay.

More than $10m still has to be found for the UN's contribution to three years of tribunal work.

Cambodia's government has also asked for help to fund its commitment to the tribunal.

Last December, the UN and the Cambodian government agreed on a budget of $56m.

Three-quarters of that will come from the UN, the remainder from Cambodia.

But so far, donors have been slow to come forward.

On Friday, Canada became only the fifth country to pledge cash to the UN.

The pledging conference aims to change that situation.

Time pressure

Cambodia has sent a three-person delegation to New York to press their claims. They will point out that speed is of the essence.

Most of the surviving former leaders of the Khmer Rouge are now in their 70s.

"It's important to understand that if we continue to delay the process, many survivors will die without seeing justice being done, and many prime suspects and perpetrators will die without being punished, which will be very difficult for many Cambodian people trying to move on with their lives," said Youk Chang, director of the Documentation Centre of Cambodia - an organisation that investigates Khmer Rouge history.

But even if the UN succeeds in raising the required amount, there still remains the problem of Cambodia's contribution.