Prime Minister Stephen Harper has an opportunity to build a strong personal relationship with President Barack Obama when he visits Ottawa on Thursday, and it could greatly improve diplomatic relations between the U.S. and Canada, says a former ambassador.

"I don't expect any earth-shattering decisions, but establishing a relationship and putting Canada first can not be underestimated. This is a very important moment for all of us and I'm excited," James Blanchard told CTV's Power Play on Monday.

Blanchard, a former governor of Michigan, served as the U.S. ambassador to Canada for three years during the Clinton administration.

He said Obama is very well-informed about Canada, but the briefing he will receive before his visit will likely reinforce the deep ties between the two countries.

"He will be in more well-informed about the relationship with Canada, whether it's the importance of autos, the role in Afghanistan, maybe how you can be helpful in the Middle East and what your stimulus package looks like," he said.

"This is going to be huge and he will be very well briefed."

Keeping Canadian-U.S. trade flowing freely will be at the top of the agenda during the meeting.

Obama's short trip to Canada, which is expected to be only a few hours long, will include meetings with Harper and Liberal Leader Michael Ignatieff, and topics of discussion will likely include the economy and environmental issues, according to a trade expert.

However, Obama is set to sign his massive $787 billion economic stimulus legislation on Tuesday, and Canadian officials are also likely to bring up the bill's controversial "Buy American" clause.

According to Canada-U.S. trade expert Colin Robertson, Harper is expected to remind Obama about the close ties the two economies share.

"We are the most successful trading relationship in the world and we should be a model to the others," Robertson said Monday on CTV's Canada AM. "One of the challenges we face, particularly since 9-11, has been the thickening of the border and it runs counter to the economic forces between the two countries."

The "Buy American" clause calls for only American steel and iron or to be used in infrastructure projects funded by the bill.

However, officials within the Obama administration have said it does include exemptions for some foreign products, in keeping with the U.S.'s international trade agreements.

On Sunday, International Trade Minister Stockwell Day said that Harper will likely press upon Obama the importance of keeping away from protectionist policies during the current economic downturn.

"Our intent and our resolve is to see that there is no increase of that 'Buy American' act and the provisions of it ... we don't want to see an expansion of protectionism and that's the territory that we're going to be marking out and I'm sure that the prime minister will be sharing some of those things with the president," Day said during an interview on CTV's Question Period.

According to Robertson, about 80 per cent of Canadian trade goes to the U.S., which means Canadian officials must work hard to ensure the border stays open to Canadian products.

"The main point of this visit is for the two leaders to get to know each other and for the president to leave Canada with a sense that this is a responsible country, a good ally, a neighbour, a place with whom we can do business and on whom we can rely upon," Robertson said.