With the fate of the proposed Keystone XL pipeline still in the hands of U.S. President Barack Obama five years on, Prime Minister Stephen Harper told a crowd of business leaders gathered in New York that he will not take no for an answer.

Harper, who participated in a question and answer session with the Canadian American Business Council on the second day of his visit to New York Thursday afternoon, said in no uncertain terms "my view is you don't take no for an answer."

"We haven't had that but if we were to get that, that won't be final. This won't be final until it's approved and we will keep pushing forward," Harper said in his strongest statement on the proposed cross-border pipeline to date.

The event was moderated by CNBC anchor Maria Bartiromo.

Asked by Bartiromo when he last spoke to Obama about the Keystone XL pipeline, Harper said he has been in touch with the U.S. president "very regularly" on the matter.

"The president has always assured me that he'll make a decision that's in, what he believes is, the best interest of the United States based on the facts. I think the facts are clear, " Harper said.

'The logic behind this project is simply overwhelming'- Prime Minister Stephen Harper on the proposed Keystone XL pipeline

The prime minister touted the economic and environmental benefits of the Keystone XL pipeline to both countries, saying "the logic behind this project is simply overwhelming."

Harper cited the U.S. State Department's own finding that showed "the environmental impacts of the Keystone [XL] pipeline are negligible."

Critics denounce Harper's approach 

NDP Natural Resources critic Peter Julian said Harper's pitch had a "desperate" tone to it.

The proposed Keystone XL pipeline "has gone from a ‘no brainer’ to a major irritant in Canada’s relationship with our closest trading partner — all because the Conservatives refuse to address the environmental impacts of oil sands development," Julian said.

Asked by the moderator why Obama was still sitting on the decision, Harper said "it's just politics."

His candour appeared to surprise the business leaders who could be heard laughing in the crowd, albeit briefly.

Harper went on to say that "bad politics make bad policy."

"I believe that in strong, advanced countries and economies like ours bad policies ultimately get reversed," Harper said, adding that there is no "plan B."

Liberal Natural Resources critic Geoff Regan was also critical of Harper's comments, describing them as "bizarre."

"Conservative mismanagement of the Keystone XL pipeline is costing Canadians’ jobs and damaging our relationship with our most important trading partner," Regan said.

Harper letter to Obama

TransCanada's proposed Keystone XL pipeline would carry Alberta's crude oil south to refineries in the U.S. Gulf Coast.

As CBC News reported on Sept. 6, Harper sent a letter to Obama formally proposing "joint action to reduce greenhouse gas emissions in the oil and gas sector," if that's what is needed to gain approval of the Keystone XL pipeline.

Canada has redoubled its lobbying efforts with ministers and premiers travelling south of the border in recent weeks and months to tout the merits of the pipeline.

Earlier in the day, Harper met 16-year-old Malala ​Yousafzai, a Pakistani teen who became a champion for girls' education. Yousafzai was shot in the head by the Taliban last fall and later recovered in a British hospital.

Harper tweeted a photo of his meeting with her saying that he, "had the honour of meeting Malala this morning. Her courage & strength serve as an inspiration to us all."

On Wednesday, Harper announced that part of the money Canada pledged during the Muskoka Initiative in 2010 will go to nine projects that will improve the health of women and children in developing countries.