Couillard told The Associated Press on Tuesday he doesn't see much economic benefit for Quebec if his province is simply a "transit place" for oilsands crude making its way to the East Coast.
But New Brunswick Premier Brian Gallant said the pipeline project will create jobs and help grow the economies of all the provinces.
"It's going to be our role — myself and others who support this project and want to see this investment be made — to show New Brunswickers, to show Quebecers, to show Canadians across the country that there are benefits for all of us, that it can be done safely and can be done in a way we all have benefits," Gallant said Wednesday.
TransCanada Corp.'s (TSX:TRP) proposed $12 billion project would ship crude 4,600 kilometres from Alberta to Saint John, N.B.
TransCanada initially planned to also build a marine terminal in Cacouna, Que., but scrapped the plan because of concerns over beluga whale habitat.
The company says it's looking for another Quebec site and has pushed the pipeline's startup date back by about two years from the original 2018 target.
Couillard's doubts about the project centre on its benefits to Quebec but he also expressed his concerns about shipping crude by rail in his interview with the AP in New York.
"We've seen unfortunately and tragically in Quebec that rail transport is not necessarily the safest way to go," said Couillard, referring to the runaway oil train that exploded in Lac-Megantic, Que., killing 47 people nearly two years ago.
"I prefer a world without fossil fuel, only electric, you know," he added.
New Brunswick Energy Minister Donald Arseneault said the pipeline is the safest way to move the oil across the country to get it to market.
"Premier Couillard as well as all the other premiers across the country understand the importance of making sure we get the oil from Alberta to market, and the pipeline is a safe route when you compare it to, maybe, other means of transportation and I think he truly understands that," he told reporters in Fredericton.
Arseneault said he's confident the project will be completed.
"I see this going forward and TransCanada is working with all stakeholders including the province of Quebec to make sure that happens," Arseneault said.
Energy East would make use of an existing natural gas pipeline for roughly two thirds of the way, with new pipe being built through Quebec and New Brunswick. It would ship up to 1.1 million barrels of crude a day.
While TransCanada is now weighing its options for a different Quebec site for a marine terminal, CEO Russ Girling has said having just the one terminal in Saint John is a possibility as well. It expects to make a decision toward the end of the year.