WASHINGTON/NEW YORK (Reuters) - A French emissions exchange and a Chinese group are forming a carbon market standard for China, marking a step toward a voluntary system to limit greenhouse gas emissions from agriculture and forestry in the world's top emitter.

The French company BlueNext, 60 percent owned by NYSE Euronext, and the China-Beijing Environment Exchange (CBEEX), a government-backed program, formed the standard which they hope to eventually expand to cover voluntary emissions reductions in Chinese transportation, construction and manufacturing.

"If you want to set up a credible and reliable (voluntary emissions reduction) market you need a standard," David Rapin, a BlueNext official, told reporters in New York on Wednesday.

"A standard is a set of rules in order to ... develop infrastructure in order to have clear emissions reductions with transparency," he added.

Voluntary carbon standards provide a framework for developers of clean projects, such as reducing deforestation or storing carbon in soil through no-till farming, to get emissions reductions verified. They can also lead to the creation of credits that can be sold in voluntary emissions markets.

The groups hope the standard will be a first step in bringing investments from Chinese companies in such projects and American firms that find it easier to pay others to reduce emissions, rather than cut their own, the groups told reporters.

China's per capita emissions are much lower than those of the United States, the world's second leading emitter.

The groups also hope to eventually set up a trading platform in Beijing.

More details about how the standard will work will be released during U.N. climate talks in Copenhagen in December.

Companies are racing to expand carbon markets in China ahead of the meeting in Copenhagen when 190 countries will try to hammer out new deal on global warming to succeed the Kyoto Protocol. The talks are bogged down on how to share the burden between rich and poor countries on taking actions to reduce emissions.

The Chicago Climate Exchange, which is owned by UK-based Climate Exchange Plc has signed a deal to set up a Chinese emissions exchange, but has declined to say how much it will invest or when trading might start.

Trade in the global voluntary market, mostly driven by companies looking to reduce their carbon footprints ahead of expected compulsory emissions rules, more than doubled last year to more than $700 million, according to a report in May from New Carbon Finance and Ecosystems Marketplace.

CBEEX Chairman Xiong Yan called on developed nations to help China defeat the "common enemy" of climate change.

"Support between countries has to be fundamental," he said, adding that countries such as Japan and the United States must share technology with developing nations to help reduce emissions.

(Editing by Christian Wiessner)