The deal, if completed, would mark the first outright takeover of a large Canadian energy producer by a Chinese state-owned enterprise.

The ambassador also said negotiating a full free-trade agreement within a decade would be the best way of assuring fair, two-way trade and investment between China and Canada.

“It’s time to open up each other’s markets,” Zhang said in remarks that coincide with Chinese Commerce Minister Chen Deming’s visit to Canada. “It’s high time to do the exploratory work on the possibility of a free-trade agreement.”

The newspaper said it was the first time that a senior Chinese representative called for early, accelerated talks on a free-trade deal.

Concern that China has unfairly limited Canadian companies from investing there is one of the issues affecting the debate within Canada on whether the government should approve CNOOC’s bid for Nexen.

Industry Ministry officials are looking closely at the bid to determine whether it is of net benefit to Canada.

CNOOC, whose offer has already been endorsed by Nexen shareholders, said it did not expect Chen to raise its sensitive takeover bid during talks with the Canadian government.

But Canadian Trade Minister Ed Fast fully expects to discuss ways to expand Canada’s relationship with China when he meets with Chen on Sunday, Fast’s spokesman said on Saturday.

“Canada wants to continue to expand its relationship with China, but we want to see it expand in a way that produces clear benefits for both sides,” spokesman Rudy Husny said in an e-mailed statement. “Minister Fast will continue this discussion when he meets with his counterpart [on Sunday] in Vancouver.”

Canada’s priority is to remove what it considers to be Chinese trade barriers on goods and services, and increase exports such as lumber, grains, beef and value-added products, Husny said.

In the interview, Zhang said a free-trade treaty would go a long way towards expanding trade and investment between the two countries, an important goal for Canadian Prime Minister Stephen Harper.

Harper wants to ease the dependence of Canada’s export-oriented economy on the United States, its main trade partner.

Although Canada is seeking substantial foreign investment in its oil and gas industry, the CNOOC move is raising concern inside the cabinet, where some members are wary of letting a Chinese state-owned enterprise buy up domestic assets.

Zhang said Canadian fears over China’s intentions are unfounded. “We are not coming to control your resources,” he said.