UPDATE 1-CNOOC-Nexen deal wins key U.S. regulatory approval

TORONTO, Feb 12 (Reuters) - U.S. regulators have approved the $15.1 billion takeover of Canadian oil and gas company Nexen Inc by China's state-owned CNOOC, removing the final barrier to China's largest foreign takeover.

Calgary, Alberta-based Nexen said on Tuesday the Committee on Foreign Investment in the United States (CFIUS) has approved the deal. The companies had been awaiting U.S. approval of the deal because Nexen has assets in the Gulf of Mexico, as well as in Canada and other countries.

Canada gave the contentious deal a green light late last year, but indicated it would not allow further acquisitions in the strategic oil sands sector by foreign state-owned companies.

The United States has traditionally been more wary than Canada of Chinese investment, prompting some speculation that Washington might want Nexen to dispose of the U.S. assets.

In 2005, the United States, blocked CNOOC's bid for Unocal Corp because of national security concerns, and an influential House committee last year urged U.S. companies not to do business with Chinese telecommunications firms like Huawei and ZTE for fears that China could use equipment made by the two to spy.

In a brief statement, Nexen said it now expects the deal to close in the week of Feb. 25. It gave no indication that the CFIUS panel had made any demands around divestitures.

CNOOC first bid for Nexen on July 23 last year.