Prime Minister Stephen Harper says he's found a partner in Barack Obama when it comes to green policies, on the eve of the president's arrival in Ottawa.

Harper defended his environmental record Wednesday on CNN, going so far as to blame former president George W. Bush for blocking efforts to fight climate change, and said Obama looks to be a much more willing partner.

"We've been trying to do so in an integrated economy when the United States has not been willing to do so. I think quite frankly that we have the present administration that wants to see some kind of regulation in this is an encouragement," Harper said Wednesday.

But environmentalists say that Harper is only acting now because Obama has made a number of green moves only weeks into his presidency.

Mike Hudema of Greenpeace told CTV News that his organization has seen more positive environmental signs in the "first three weeks of Obama than in three years of a Harper legacy."

Obama and Harper are expected to start the framework for negotiations for a common North American strategy to cut greenhouse gas emissions.

Environment Minister Jim Prentice said that the two countries need to "to clean up the way we produce energy whether its coal or oil sands or other forms of hydro carbon."

But there are worries among the Canadian oil sector because the Obama administration has said it wants to cut down on "dirty oil," which may include Alberta's oil sands. That topic is expected to come up Thursday.

Harper issues warning

Harper also issued dire warning that U.S. protectionism could turn a recession into a depression Wednesday.

He said that any effort to close the U.S. border to trade would be a "huge risk to the world."

Harper also made mention of a topic he doesn't want to discuss with Obama - reopening the North America Free Trade Agreement to debate.

He said reopening NAFTA could mean never-ending re-negotiations. Obama raised fears of re-negotiating NAFTA during his campaign for president, but has since then quietly backed off that initiative.

Obama's talk of reopening NAFTA was believed to be mostly aimed at Mexico, but Harper said that even by putting one part of the agreement under the microscope could put the entire deal in jeopardy.

When asked by CNN's Wolf Blitzer about what advice he could give the U.S. on the economy, Harper declined to do so.

But he did tout Canada's strong banking system and said that his country's economic issues were nowhere near as significant as the U.S.'s.

'Fruitful' discussion expected

Harper said he expects to have "fruitful" discussions tomorrow with U.S. President Barack Obama on the economy, international affairs, the environment and energy issues.

"All of those things along with the border, the great border we share that is obviously the transitway for the largest trade flows in history -- those will all be very important topics we will be discussing," Harper told CTV Toronto in an interview that aired Tuesday night.

Obama's much-anticipated visit will also be the first international state trip he has made since his inauguration, and thousands of people are expected to gather on Parliament Hill in hopes of seeing him.

"I'm hoping it will be the beginning of many fruitful discussions between the two of us and obviously between our governments," Harper said.

Obama and Harper are expected to talk about the recent developments in the struggling auto sector and how their respective governments will respond.

Charles Doran, director of Canadian Studies at John Hopkins University, told CTV Newsnet that North America's integrated auto sector requires an integrated governmental response.

"They want to be sure they don't get in each other's way (with an auto bailout), they want to be sure there isn't a lot of resistance on each side in terms of protectionism," Doran said Wednesday. "A lot of things need to be discussed to make this work."

Doran said that Obama's visit will demonstrate a significant change in foreign policy from the previous U.S. administration.

"What we see here is a difference in tone. This is a new administration in the U.S. that takes the position that Canada and other countries are part of world order . . . and (Obama's) government is listening," he said.

Obama visit excites Canadians, Harper included

Even though Obama's visit will be brief and crammed with official events, busloads of well-wishers are expected to come from Montreal, Toronto and Kitchener, Ont.

Groups plan to line the fenced-in lawn at Parliament Hill as well as the route Obama's motorcade will follow. Also, a "Yes We Span" march is planned for the Laurier bridge.

Harper's staff were anxious this week to point out that the two leaders have a lot in common, saying they are similar in age, both have young families and neither had been in elected office for long when they became their nation's leader.

"They really, at a basic level, have quite a bit in common," Harper spokesman Kory Teneycke told The Canadian Press, pointing out that both come from "outside the political establishment."

One of the main things they share, Harper said, is the challenge of fixing the crippled global economy, achieving success in Afghanistan and addressing environmental and energy concerns

Harper has spoken with Obama three times and described him as "very easy to talk to."

He said he is looking forward to meeting the president in person for a more extended visit.

"The conversations I have had with him haven't been lengthy, but we've covered a lot of ground. He's been very focused on what his agenda for the fall is, what he wants to achieve. Obviously we're going to have many more hours when he's here on Thursday."

Harper said he believes the Obama administration has a "great sense" of the importance of the Canada-U.S. relationship, and the potential to build on it.

Itinerary details

Obama's plane will be landing at Hangar 11 at Ottawa international airport at about 10:30 a.m., where he will be greeted by Gov. Gen. Michaelle Jean followed by a short, private meeting.

After that, Obama's motorcade will travel to Parliament Hill where thousands of well-wishers are expected to be waiting outside a security fence, hoping for a glimpse of the president.

The two leaders will have a 10-minute one-on-one meeting, then a "restricted" meeting with senior officials, followed by a working lunch with officials.

They will then make statements to the media and take a total of four questions before Obama returns to the airport, where he will meet briefly with Liberal Leader Michael Ignatieff.

Finally, Obama will climb aboard Air Force 1 and head home at about 4:30 p.m.

With a report by CTV's Robert Fife