"There's every reason to not give up on this file and (to) continue to pursue every possible reasonable way in which to make our case," Ken Hughes told reporters at an Economic Club of Canada summit on Friday.
"Until it's over, it's not over. You have to be in the game. You have to keep making the case."
TransCanada Corp. (TSX:TRP) first applied for a U.S. presidential permit to build the $5.4-billion pipeline more than five years ago. The company is hoping a final U.S. State Department decision on the line will come early next year.
The project has become a major focus for the U.S. environmental movement, which has raised concerns over the pipeline's role in enabling oilsands development and its potential environmental impact in the event of a spill.
In his speech, Hughes stressed the need to get access to markets not just to the south, but also to Canada's east and west coasts by building pipelines.
Alberta Premier Alison Redford is to make her fifth trip to Washington next week. Plans are to meet with State Department officials to talk about Keystone XL.
Federal Natural Resources Minister Joe Oliver was in Washington this week stumping for Keystone and in September Prime Minister Stephen Harper told a New York business audience that pipeline supporters must not "take no for an answer."
TransCanada CEO Russ Girling said he appreciates Redford going to Washington to speak to the province's largest oil customer.
"That relationship has been built over the last 50 or 60 years and will still be there for the next 50 or 60 years," he said.
"We're going to continue to be their largest supplier of imported oil and they're going to continue to be our largest customer. This isn't the last time a premier will be going there."
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