Nexen Inc (NXY.TO) and China's CNOOC Ltd (0883.HK) said they have mutually agreed to extend the closing date of CNOOC's takeover of the Canadian oil and gas producer by 30 days to March 2, 2013.

Nexen said in a statement it would also postpone the release of its 2012 fourth quarter financial results. It did not give a date for the release of the results.

CNOOC Ltd said in late December that it expects its $15.1 billion takeover of Nexen to close in the first quarter of 2013 at the earliest, a move that could be related to giving U.S. regulators more time to approve a sensitive aspect of the deal.

The company is still awaiting U.S. approval over its purchase of Nexen assets in the Gulf of Mexico after Canadian officials approved the deal last year.