CME Group Inc, the biggest operator of U.S. futures exchanges, on Thursday filed an application with London financial authorities to launch a European market next year offering currency futures.

CME is looking to expand internationally as regulators worldwide push more of the vast over-the-counter derivatives market onto regulated exchanges.

CME has had a London-based clearinghouse since May 2011 that handles energy and other swaps, but this is the first time the exchange giant has sought to open an exchange abroad.

In its filing to the Financial Services Authority in London, CME said it plans to offer 30 currency pairs at first and expand into other asset classes "over time." It plans to open the doors of its electronic, London trading venue in mid-2013, the filing said.

Britain's Office of Fair Trading has opened a formal six-week inquiry into its application.

(Reporting by Ann Saphir; Editing by Kenneth Barry)