Cambodia's UN-backed genocide tribunal is expected to dismiss two new cases against Khmer Rouge suspects in the face of ongoing political pressure, court observers say.

The Extraordinary Chambers in the Courts of Cambodia (ECCC), dogged by allegations of political interference and strapped for cash, has yet to announce whether it will go ahead with a third and fourth case against five unnamed members of the brutal 1975-1979 regime. 

But court monitors say a decision is expected in the next few weeks.

"Right now, all of the information we have suggests an imminent dropping of the cases against these five suspects," Clair Duffy from the rights group Open Society Justice Initiative told AFP.

Cambodian Prime Minister Hun Sen - himself a mid-level Khmer Rouge cadre before turning against the movement - has repeatedly voiced opposition to further trials, saying they could plunge the country back into civil war.

Late last year, the premier even told visiting United Nations chief Ban Ki-moon that new cases were "not allowed".

"Any decision to dismiss these cases will have profound implications for the legacy of this court," said Duffy.

She added the move "may just show to the world that even with UN-backing and international funding, the Cambodian government could still control the court's docket".

Anne Heindel, a legal advisor to the Documentation Centre of Cambodia, which researches Khmer Rouge atrocities, said if the cases were dropped, the international community would have to shoulder some of the blame.

"Neither the UN nor state donors have vocally supported the court's judicial independence in the face of bellicose government statements," she told AFP.

In its landmark first case, the court sentenced former prison chief Kaing Guek Eav, better known as Duch, to 30 years in jail in July for overseeing the deaths of 15,000 people.

Both the defence and the prosecution appealed against the punishment last week and a ruling is expected in late June.

The tribunal also indicted four of the regime's most senior surviving leaders, including "Brother Number Two" Nuon Chea, over the deaths of up to two million people. Their joint trial is due to start later this year.
Cambodian and international co-prosecutors have openly disagreed on whether the court should go after five more suspects.

"The investigation in cases three and four is ongoing and remains confidential," said ECCC spokesman Lars Olsen, who dismissed Duffy's words as "pure speculation and gossip".