Canadian regulators extended the review period for acquisition for a third time to Dec. 10, saying more time was needed for an adequate consideration.
China National Offshore Oil Corp. in July offered to take over Nexen for $15 billion. Around 90 percent of the Nexen shareholders voted in favor of the deal. Terms of the agreement with CNOOC, however, are subject to the approval of the provincial government of Alberta.
Canadian Ambassador to China Guy Saint-Jacques said the government was reviewing the proposal a final time.
"I am confident we will have a decision by Dec. 10," he was quoted by Bloomberg News as saying. "It's a very important deal and it's now being fully considered."
Alberta Deputy Minister for Energy Jim Ellis was quoted as saying he was "positive" the deal would go through.
Last month, Malaysia's state-owned energy company Petronas said it scheduled meetings with Canadian officials to address concerns about a takeover bid for Canada's Progress Energy. Canadian Minister of Industry Christian Paradis has said in a letter to Petronas that he was "not satisfied" the $6 billion bid was in the national interest.