The New York Mercantile Exchange, the world's largest energy futures exchange, has rejected a $980m (€799m) offer from private equity firm, Parthenon Capital, will continue to explore merger possibilities.

Parthenon's April offer for a 60% stake, which valued Nymex at $1.6bn, fell through after several months of discussions and the reshuffling of the exchange's senior management. The breakdown of talks followed the appointment of Merrill Lynch as adviser to the exchange. It's review of strategy is ongoing.