The Government has pledged a extra $200,000 to support Cambodia's war crimes tribunal.

Prime Minister John Key announced the funding during a visit to the Khmer Rouge tribunal in Phnom Penh today.

Cambodia is notorious for its Khmer Rouge ''killing fields'' and the genocide of up to two million people under the brutal Pol Pot regime in the 1970s.

Since 2007 the UN-backed courts have worked since 2007 to bring the living Khmer Rouge leaders to justice.

Former Governor-General Dame Sylvia Cartwright has been a judge since 2008.

The cash injection adds to $100,000 pledged by Foreign Minister Murray McCully earlier this year taking New Zealand's contribution to $1.2 million.

Key said the tribunal is helping Cambodians move on "from a particularly dark period in their history".

In August it was reported the war crimes tribunal is near collapse because it is running out of cash. The Euro-zone crisis, Japan's earthquake and shrinking global budgets saw contributions drying up and it needed NZ$112m for 2012/13 running costs.

Key was in the Cambodian capital for the East Asia Summit. Today he will fly to Yangon for the first visit of a New Zealand to Myanmar.

Talks with President Thein Sein and opposition leader Aung San Suu Kyi  will show  support for the move to democracy in Myanmar, which spent decades under oppressive military rule.

- © Fairfax NZ News