* ICE becomes a majority shareholder of the gas unit
* Dutch TenneT to be a majority owner of the spot power unit
* Belgium Fluxys says will exit the exchange ownership
AMSTERDAM, Sept 17 (Reuters) - IntercontinentalExchange has bought a majority stake in the spin-off gas and power derivatives business of Amsterdam-based bourse APX Endex, giving the U.S. exchange better access to western European energy markets pegged for huge growth.
ICE made a cash-funded offer for 79.12 percent of the gas and power derivatives business which offers trading in the growing Dutch gas market and from the end of September the Belgian spot gas market, areas that are set to gain from rising gas demand in Europe.
The remaining shares in the business, which will continue offering power futures trading, will be held by Dutch gas network operator Gasunie.
ICE currently offers its own products in the European power and gas markets, but most liquidity has focused on Britain's NBP gas market, where the APX Endex business has low market share.
A spokeswoman for ICE said it was too early to comment on how the products would be integrated and whether the entity would operate under a new name.
The parties involved did not disclose the value of the deal, which is expected to close at the end of the first quarter of 2013 pending regulatory approvals.
The APX Endex spot power business will continue operating under main shareholder TenneT, the Netherlands' power grid operator, which will own 70.84 percent next to Belgium's Power network company Elia.
"Now is a good time to split the company and allow the gas part and the electricity part to consolidate separately with partners for further strengthening," Mel Kroon, TenneT's chief executive, said in a statement.
Belgian gas grid operator Fluxys, which owned 3 percent of APX Endex, has exited the business.
"We thought it was not part of our core activities, of course we stay working together with the exchange," a Fluxys spokesman said.
Before the restructuring TenneT owned 56.1 percent of APX Endex, Gasunie held a 20.9 percent stake, while Elia had 20 percent and Fluxys had 3 percent.