Americans face a "stark choice" to keep importing heavy crude from unfriendly countries with far worse environmental records than Canada or opt for the controversial $7-billion Keystone XL pipeline to funnel Alberta's oil sands crude to Gulf refineries on the Texas coast, Natural Resources Minister Joe Oliver said Wednesday.

"The U.S. can choose Canada – a friend, neighbour and ally – as its source," Mr. Oliver said in a speech in Washington, the latest in a long string of public lobbying by premiers and federal ministers. "Or it can choose to continue to import oil from less friendly, less stable countries with weaker – or perhaps no – environmental standards," he added, repeatedly fingering Venezuela as the prime example of an unreliable, unfriendly and less-than-green source of thick, carbon-heavy crude.

In a post-speech question-and-answer session at the Center for Strategic and International Studies, the minister dropped his usual carefully measured tone to decry leading climate-change scientist James Hansen, recently retired from NASA. Developing the oil sands, Mr. Hansen has said, would mean "there is no hope of keeping carbon concentrations below 500 (parts per million), a level that would, as earth's history shows, leave our children a climate system that is out of their control."

Story continues below advertisement

The minister said such doom and gloom predictions were "exaggerated rhetoric," that "doesn't do the (environmentalists') cause any good."

"Frankly, it's nonsense," Mr. Oliver said, adding that Mr. Hansen "should be ashamed."

Mr. Oliver's delivered his speech to a carefully screened audience, apparently to avoid anti-Keystone demonstrators that disrupted a similar event earlier this month when Alberta Premier Alison Redford was repeatedly heckled by protesters, one of whom was tackled as he charged the stage.

On Wednesday, the dozen or so anti-Keystone protesters were left outside on the sidewalk while Mr. Oliver spoke to fewer than 100 people at a CSIS Energy and National Security session.

Sounding mostly familiar themes, Mr. Oliver said the U.S. – despite soaring domestic production – will still need imported oil for decades to come and that Canada's vast oil sands offered the best source.

"We would never turn our back on the United States," the minister said, pointedly noting that Venezuela has repeatedly threatened to cease exporting crude to Gulf refiners.

In fact, Mr. Oliver painted a rosy picture of an energy-independent North American that – within 20 years – would have no need for any overseas oil.

Story continues below advertisement

"No more reliance on unstable or irresponsible producers, no more cartels – only the security and confidence of knowing you are dealing with a friend who shares your democratic values, your belief in the free market and has a proven and growing commitment to environmental and social responsibility," Mr. Oliver said.

Given the strategic importance the United States attaches to key allies – such as Saudi Arabia – in pivotal areas of the planet such as the Middle East, the notion of any government in Washington picking oil suppliers on democratic values seems unlikely.

Mr. Oliver also rejected the claims of anti-Keystone XL groups that thwarting the $7-billion pipeline would result in keeping Alberta's massive oil sands – considered perhaps the third-largest untapped reservoir on the planet – locked forever in the ground and uneconomic.

That no Keystone "would be some kind of body blow to the oil sands is just plain wrong," he said, adding that Canada had ambitious plans to build pipelines to get oil sands crude to seaports on both the east and west coasts where it will be shipped to India, China and other fast-growing markets.