Harper made the pipeline pitch while taking questions at the Council on Foreign Relations in New York City.
He laid out the case for why U.S. President Barack Obama's administration should approve the proposed pipeline that would connect Alberta's oilsands to the Gulf Coast, touting job creation prospects. Harper said the project will create 40,000 jobs south of the Canadian border and that can't be ignored.
"This is an enormous benefit to the U.S. in terms of long-term energy security," Harper added.
He acknowledged environmental challenges, but said that the intensity of greenhouse gas emissions attributed to the Alberta oilsands have dropped by 25 per cent over the last decade and that the government is continuing to invest in technology to further reduce emissions.
The prime minister also said that the amount of emissions from the oilsands plays a small part in total global emissions.
"It's almost nothing globally," he said, adding later that Canada is a small contributor compared to other big oil producers such as Venezuela.
"I don't have to tell you there are probably reasons beyond just emissions why you would want to have your oil from Canada rather than Venezuela," he said.
Harper said when all the economic and other factors are weighed, it's clear why there is such broad support for the Keystone XL project in the U.S.
Technology key to cutting emissions
"I think this absolutely needs to go ahead but you can rest assured that making our emissions targets including in the oilsands sector is an important objective for the government of Canada," he said.
The pipeline needs Obama's approval because it crosses the Canada-U.S. border. Harper said it's either going to be pipelines or railways that bring Canadian crude oil to the U.S. and that railways would be more challenging to the environment than pipelines that are properly built.
"I think all the facts are overwhelmingly on the side of approval," said Harper. "I know the administration will do a thorough analysis before arriving at the right decision."
Harper and members of his cabinet have been making repeated trips to the U.S. over the last few months to push for the project's approval. But those opposed to it say further development of Alberta's oilsands and the pipeline will have damaging effects on the environment, including increased greenhouse gas emissions. Anti-Keystone protesters were outside Harper's event.
This week, in advance of the prime minister's appearance at the Council on Foreign Relations, the government took out ads in U.S. publications and launched a new website to promote its sector-by-sector regulatory approach to reducing emissions.
Harper took several questions on the environment, climate change, and Canada's withdrawal from the Kyoto Protocol.
He said his government favours a mandatory international protocol that includes all major emitters and that new technology is the key to tackling global emissions.
"That is the thing that will allow us to square economic growth with emissions reduction and environmental protection. I am convinced if we cannot square those two things we're not going to make progress globally," he said.
On other topics:
- Harper was asked about a national inquiry on missing and murdered aboriginal women and said that his government has funded studies and is encouraging action to improve the status of aboriginal women in their communities. He said he is skeptical of commissions of inquiry.
- Harper said that external factors remain the biggest risks to Canada's economy and that the government is making progress on improving Canada's productivity.
- Arming the opposition in Syria is "risky" according to Harper and Canada wants a diplomatic solution to the conflict.
- The G20 often fails to grasp the holistic approach that needs to be taken on global issues.
- Canada wants foreign investment but doesn't want to see sectors "nationalized" by state-owned enterprises.
Harper told the audience that Canada's economic fundamentals are strong and although growth is slow, it's steady. He outlined steps his government is taking to improve growth including immigration reforms and trade deals.
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