UPDATE 2-CME Group tightens grip on US futures business

(Adds comments from conference call, details, changes dateline, prev PHILADELPHIA)

By Ros Krasny

CHICAGO, March 17 (Reuters) - CME Group Inc CME.N, the world's largest derivatives exchange, on Monday tightened its grip on U.S. market share by announcing a definitive agreement to buy energy and precious metals mart NYMEX (NMX.N: Quote, Profile, Research) for about $9.4 billion.

The terms of the deal were unchanged from CME's original bid on Jan 28, but the overall price tag dropped from the original $11 billion offer due to the fall of CME's stock price -- a decline that steepened on Monday.

Each share of NYMEX will be exchanged for 0.1323 shares of CME Class A common stock and $36 in cash. That values NYMEX at about $91.66 per share.

Shares of both companies were savaged on news of the deal. NYMEX shares fell to their lowest level since its initial public offering in November 2006, while CME fell to its lowest level in more than two years.

The deal, which company officials expect will close by year end, marks the latest merger in the quickly consolidating market of U.S. and global financial exchanges.

It will give CME Group a 95 percent market share in the U.S. futures and options-on-futures business.

CME Group was created in July 2007 when Chicago Mercantile Exchange Holdings bought the Chicago Board of Trade for about $12 billion.