Prime Minister Stephen Harper took his message on Canada's oil exports to an American audience Monday, arguing the two countries have different interests when it comes to energy.

Speaking at the Wilson Center following trilateral talks with the U.S. and Mexico, Harper addressed the budget, as well as a plan to streamline the approval process for resource development, and to bring Canada's books back into balance by 2015-16.

The Canadian government isn't going to change course on a plan to increase oil exports to Asia, even if the U.S. approves a plan by TransCanada to build the Keystone XL pipeline, he said.

Energy security for Canada has never meant the same thing as it does for the United States, Harper said, adding the two countries have different interests.

"We cannot be, as a country, in a situation where really our one and in many cases only energy partner could say no to our energy products," he said, adding that Canadian oil is sold at a discount because the country is "a captive supplier."

"For us, the United States cannot be our only export market. That is not in our interest, either commercially or even as I say in terms of price."

Harper seemed relaxed in front of the audience, taking questions from Wilson Center President Jane Harman. The wide-ranging talk hit on a number of hot topics, including the ongoing bloody battles in Syria between the government and its opponents.

On Syria, Harper said the opposition doesn't look strong enough to overthrow the government of President Bashar Assad. He called on the opposition to show unity and strength, and on Assad to step down.

On the environment, Harper said carbon offsets are a bad way to deal with emissions. Offsets are a way of pretending you're addressing emissions when you're really not, he said.

Trade a major focus of talks

Earlier, the leaders of Canada, the U.S. and Mexico focused on their economies and security in trilateral talks Monday, but Harper showed no sign of budging on one item that could deny Canada entrance into trade talks with Pacific nations.

Harper, Mexican President Felipe Calderon and U.S. President Barack Obama spoke to reporters following a meeting where they talked about transnational organized crime and how to keep increasing trade.

Obama says he's pleased that Canada and Mexico want to join the Trans-Pacific partnership free trade talks, along with nine other countries including the U.S., New Zealand, Australia, Peru, Singapore and Malaysia.

But Harper showed little sign he's prepared to open up Canada's protectionist supply management system to ease entry into the talks.

Canada attaches large tariffs to dairy and poultry imports, something other countries — including those involved in the trade talks — would like to see dropped to open up access to their own producers.

Harper showed little sign Monday of wavering on the need to protect Canada's supply managed industries.

"We expect to negotiate and debate all manner of issues and we seek ambitious outcomes to free trade agreements. In those negotiations, of course, Canada will attempt to promote and defend Canada’s interests not just across the economy, but in individual sectors as well," Harper said.

Obama, however, hinted that Canada may have to be more flexible.

"Every country that’s participating is going to have to make some modifications. That’s inherent in the process because each of our countries have their own idiosyncrasies, certain industries that have in the past been protected," Obama said.

"I don’t think Canada would be unique in that. Are there areas where we’d like to see changes in terms of Canadian practices? Of course. I assure you Canada would have some complaints directed at us."

Drug trade also discussed

Harper says the drug trade is a serious problem for the western hemisphere, with a need for a transnational response co-ordinated between the countries.

What happens in each of the three countries profoundly affects the others, Obama said, adding the leaders represent nearly half a billion people.

The meeting comes two weeks before they reconvene for the Summit of the Americas in Cartegena, Colombia, from April 14-15. The Summit of the Americas meeting includes all leaders from the Western Hemisphere.

Defence ministers from the three countries met March 27 in Ottawa.

Peter MacKay, Mexican Secretary of National Defence Guillermo Galván Galván, Mexican Secretary of the Navy Mariano Francisco Saynez Mendoza and U.S. Secretary of DefenCe Leon Panetta discussed drug trafficking, joint security and disaster assistance.