In December, the RGGI states agreed to cap carbon dioxide (CO2) emissions from power plants in member states beginning in 2009 and cut them 10 percent by 2019. The RGGI hopes to form a market for CO2 in which utilities that cut emissions of the heat-trapping gas under set limits can sell credits to plants that chose not to cut emissions.

Most scientists have linked emissions of gases such as CO2 and methane to global warming which could increase the intensity of big storms and melt glaciers threatening low-lying nations.

Richard Sandor, chairman and chief executive of CCX, says voluntary US exchanges can help members get ahead of their competition in preparing for potential future US mandatory emissions caps.

"As RGGI evolves, the New York and Northeast climate exchanges will provide transparency, as well as a (link) with global greenhouse gas emissions trading," Sandor said in a release.

NO RELATIONSHIP ... YET

A person close to RGGI said the states have not yet worked with anyone to form an exchange. "There's really no relationship between the RGGI group and CCX at this point," said the source, who added that RGGI has not ruled out working with the CCX, however.

The CCX, a voluntary exchange, has about 130 members on its Chicago exchange including one of the top US utilities, American Electric Power and DuPont. Sandor sits on AEP's board.

Members in the Chicago market enter legally binding agreements to cut their emissions by a certain amount and time. If they beat those limits, they generate credit they can sell or bank. If they fall behind, they must purchase credits on the exchange.

It was not clear if the Eastern markets would operate in the same way.

Critics of the CCX point to thin trade volumes and say its trade is dominated by AEP. No big banks or major oil companies are members.

But in Europe, where emissions limits are mandatory in many countries, CCX operates the European Climate Exchange (ECX), which it says represents 85 percent of total exchange volume traded in the European Union Emissions Trading Scheme.

Members of ECX include banks Goldman Sachs, Merrill Lynch and Deutsche Bank, and energy companies including Shell and Sempra Energy Europe, a division of Sempra Energy.

The Northeast CCX trading schemes could "potentially" go beyond the RGGI plan by trading all greenhouse gases, such as methane, a much stronger greenhouse gas than CO2, a CCX spokesman said.

There were no time frames for when the two CCX trading schemes would start trading.

The states forming the RGGI are: Connecticut, Delaware, Maine, New Hampshire, New Jersey, New York and Vermont.