Vietnam, the world's second-biggest rice exporter, said Wednesday it needs help to safeguard the world's food supply from the consequences of global warming.

"The rice bowl of Vietnam will be severely affected" without action, Nguyen Khac Hieu, deputy director general of the government's climate change agency, told reporters before key global climate talks next week in Copenhagen.

"It's not only for Vietnam's sake but also for the world's food safety," said Hieu, calling for help to enable the country to adapt.

He will be part of Vietnam's delegation at the December 7-18 conference tasked with framing a new deal for tackling global warming and its impact beyond 2012, when existing commitments under the Kyoto Protocol expire.

Vietnam is planning for a one-metre (3.3 feet) rise in sea levels by 2100, which would inundate about 31,000 square kilometres (12,400 square miles) of land - an area about the size of Belgium - unless dykes and drainage systems are strengthened, says a United Nations discussion paper on climate change in Vietnam, presented at a meeting on Wednesday.

"The inundation threat is greatest in the Mekong Delta," the country's main rice production and export area, the paper said.

Many billions of dollars will be needed for Vietnam to address sea level rise and other climate change effects, the paper said, adding that the funding cannot only come from aid.

Public finance would also have to be made available, but the first step should be large investments in studies and designs over the coming decades, the paper said.

"The scale and time-span of these projects is unprecedented," it added.

Mobilising funds to help developing countries shore up defences against climate change, and to switch to an economy with low emissions of damaging greenhouse gases, will be one of the key issues in Copenhagen.