DETROIT – Given its current growth rate in the region, it is a matter of when, not if, Nissan will add North American capacity, CEO Carlos Ghosn says.

Nissan was the only one of the Japanese Big Three to gain sales and market share in the U.S. in 2011, when its Nissan and Infiniti brands took a combined 8.2% slice of the light-vehicle market, up from 7.9% in 2010.

This year Nissan in the U.S. will launch new versions of its Pathfinder SUV, Altima midsize sedan and Sentra compact car to drive growth, and aims to double the 9,674 sales of the Leaf electric vehicle recorded in 2011.

“If we continue to grow like this, we will need more capacity in the United States,” Ghosn says.

However, it will not be in the near term as Nissan still has room in its Canton, MS, plant. The auto maker’s Smryna, TN, plant, which this year adds production of the Leaf as well as the new Infiniti JX cross/utility vehicle, is almost full.

A tenet of Nissan’s Power 88 business plan is to grow U.S. market share to 10% by 2014. Elsewhere in North America, Ghosn confirms reports the auto maker will announce, in a matter of “weeks, not months,” an expansion of production in Mexico.

Nissan operates two plants in Mexico, in Aguascalientes and Cuernavaca. Reports suggest a third plant that will assemble 600,000 units annually is in the works.

Ghosn is frank when he says Nissan is underperforming in Canada. “We obviously are way below our potential in Canada,” he says, citing a mere 5% market share. “We obviously have to do a better job in Canada.”

Nissan grew sales last year in most major markets, including Japan, Europe and China. It was the top-selling Japanese brand in China in 2011, and Ghosn expects the auto maker to do the same this year in Europe.

He is optimistic about the global auto industry’s 2012 prospects, citing beleaguered Europe as the only global market that will see sales decrease.

“I don’t believe in Armageddon happening in Europe,” Ghosn says. “I think there is enough knowledge and spiritual will to solve the (sovereign-debt) problem. But it will take time.”