Lewenza said strikes at GM and Chrysler could be averted if an agreement were reached with Ford and the other two automakers gave a "firm commitment" before the deadline that they could "live with the framework" of such a deal.
Lewenza said the CAW had chosen to focus on Ford to reach a deal as the company had shown "initiative" in the past few days of bargaining, and that its negotiators had been "respectful."
"We hope to get a reasonable deal. We hope to get a modest deal," he said.
Earlier, the Globe and Mail newspaper quoted Lewenza saying that talks with Chrysler were not advancing well.
"Right now we are feeling good that we can get a deal, provided Ford continues to respond as they have in the last couple of days," Lewenza said Sunday. "Ford moved forward. But bargaining is fluid. That confidence could be shaken in an hour from now."
The union represents about 20,000 Detroit 3 auto workers.
Ford has "a strong track record of working collaboratively with the CAW," Stacey Allerton, vice president of human resources at the company's Canadian unit, said in an e-mail. "We are confident that, working together, we can find innovative solutions to help build a successful future for our Canadian operations."
GM looks "forward to continuing our discussions with the CAW," Adria MacKenzie, a spokeswoman for GM Canada, said today in an e-mail. "We are focused on working with our CAW partners to reach an agreement that will improve GM Canada's competitive position for the future."
Chrysler is "very concerned by the CAW decision," LouAnn Gosselin, a spokeswoman for Chrysler Canada, said in an e-mail. Ford isn't "in the best position to take on this role." The e-mail cited Ford's "significant reduction" in Canada. Ford closed a vehicle-assembly plant in Ontario last year.
The union's latest proposal includes a new "wage progression program" and aims to contain fixed costs while allowing the company to improve productivity, Lewenza said without being more specific. Under the current agreement, new employees start at 70 percent of the top wage and take six years to reach it.
A union goal is to secure commitments from the companies to invest in Canada, Lewenza said.
"When the companies look at future investment, labor is a piece of the pie," he said. "We want to make sure that our piece of the pie jumps out and says: 'Come to Canada.'"
The union accepted a pay freeze and gave up bonuses and time off along with other concessions as part of the restructuring that brought GM and Chrysler out of bankruptcy in 2009. GM was the last carmaker to be hit by a strike in Canada, in 1996.
A walkout "is the last tool in the bargaining toolbox," Lewenza said. "Our job is to get a deal. I'm not anxious to shut down Chrysler. I'm not anxious to shut down GM. In fact, I'm anxious to build cars so they show more profit and we're in a better position in three years."
The companies have said Canada is the most expensive place in the world to build vehicles and labor costs must fall to match their workers in the United States, or future production and investment will be put in question.
The Canadian dollar has risen about 60 percent in the past 10 years, making manufacturing more expensive in the country.
The companies have not said publicly how they propose to reduce expenses.
The union said the Detroit 3 want to permanently eliminate the cost-of-living allowance, move current and new hires to a defined contribution pension plan from a defined benefit pension plan, and eliminate a provision that allows workers to retire after 30 years under any circumstances.
The CAW offered key concessions on wages and pensions for new hires on Thursday, yielding ground that may be easier to swallow for current union members who must ratify a new contract.
In return, the CAW wants automakers to commit to investing in Canadian plants and allocating new production, ensuring members' job security.
Reuters and Bloomberg contributed to this report