The New York Mercantile Exchange is reportedly set to choose between raising capital from private-equity firms or taking the exchange public as tradable stock.

Former Nymex chairman Michel Marks confirmed Monday that in a letter sent to the Nymex board Friday he detailed a fully financed proposal to take a stake in the exchange. According to a statement, the letter said the proposal offers higher value and has “greater merit” than other proposals disclosed so far.

Final offers from potential bidders are due this week, the Wall Street Journal reported in its online edition today.

Nymex spokeswoman Anu Ahluwalia declined comment

Private-equity firms Blackstone Group and Battery Ventures VI LLP raised a joint offer for a minority stake in Nymex during the weekend to value the total exchange at US$1.3 billion, the Journal reported, citing an unnamed person close to Nymex. That tops the bid of General Atlantic LLC, whose offer for a minority stake this summer valued the entire exchange at about US$1.2 billion, the newspaper said.