Board members of the New York Mercantile Exchange are expected to be told today that a flotation of the world's largest energy futures exchange could value it at more than $1.2 billion (€980 million).

The valuation is implied by current offers for a stake in Nymex by General Atlantic, Blackstone and Battery Ventures, the private equity groups.

JPMorgan, the financial advisers to the privately owned Nymex, will make a presentation to the board saying that the exchange would fetch a higher valuation through an initial public offering (IPO).

The Nymex board is expected to make a final decision on its future ownership by the end of August, before going to a shareholder vote next month.

Nymex could be worth up to $2 billion, according to one shareholder in the third-largest futures exchange in the US, who declined to be named.

However, this would value it at more than the Chicago Board of Trade (CBOT) , the second-largest US futures exchange, which this week announced that it intends a float on the New York Stock Exchange. The planned IPO values CBOT at $1.8 billion.

Nymex could have a larger valuation than CBOT, according to the shareholder. This was because Nymex has its own trading and clearing platform, Clearport, while CBOT uses the Euronext electronic trading system and clears all trade through the Chicago Mercantile Exchange clearing system.

Last week, Nymex reported a tripling of second-quarter net income to $15.63 million on the same period a year ago.