The Keystone XL pipeline project would transport oil and gas from Alberta's oil sands to southern U.S. refineries but has brought environmental concerns, prompting President Barack Obama to defer a decision until 2013, the Calgary Sun reported.
Trump, a staunch Republican, told the Sun in an interview from Florida that Canada's Conservative government was showing better leadership.
"It's an outrage our president isn't approving the Keystone pipeline," he said. "And Canada is lucky to have superior leadership to ours."
Earlier this week, Trump also put out a tweet criticizing the Democratic president, who has been a favorite target of his.
"The Keystone Pipeline will create 20,000 jobs and lower gas prices. But Obama says no. Dumb," he wrote.
TransCanada Pipelines spokesman James Millar told the Sun he's more accustomed to hearing environmental criticism from celebrities.
"Anytime someone is going to talk about the practical benefits of this $7 billion project, regardless of what people think of Mr. Trump, it's a good thing," Millar said.
Environmentalists claim the methods used to extract the oil and gas create massive greenhouse gas emissions and fear the pipeline leak could endanger major aquifers in Nebraska.