The meeting is the second of eight which aim to secure a global climate deal by the end of next year, to come into force after the first round of the Kyoto Protocol expires in 2012.

The Bonn talks focus on the "toolkit" of steps which can curb rising emissions of greenhouse gas such as carbon dioxide, which scientists say risk catastrophic climate change.

Senior officials from more than 160 countries face the difficulty, however, that many such measures -- including carbon taxes and emissions trading -- deliberately raise energy costs by penalising carbon emissions from burning fossil fuels.

They are controversial options as record oil prices hit motorists and electricity consumers worldwide.

Meanwhile carbon-cutting biofuels have helped drive up food prices by using food crops to make an ethanol alternative to gasoline.

The United Nations' climate change chief Yvo de Boer cautioned on Sunday against blaming biofuels too much.

"While growing crops for biofuels has some influence on food prices, clearly other factors like increasing wheat consumption and hoarding of rice also play a significant role," he told Reuters.

The Bonn meeting, which ends on June 13, follows one in Bangkok in March-April which produced little of substance to contribute to a new deal.

"The challenge is now to move ahead and start identifying what could be written into the 2009 agreement," added de Boer, who is head of the U.N. climate change body (UNFCCC).

Another U.N. agency, the Food and Agricultural Organisation, hosts a summit this week in Rome to discuss record food prices.

Kyoto caps the greenhouse gases of some 37 industrialised countries, but neither of the world's top two emitters -- the United States and China.