Trade and energy will be two of the closely watched topics up for debate as U.S. President Barack Obama visits Ottawa Thursday on the first international trip since he took office.

Obama arrived at Parliament Hill shortly before noon ET for a series of short meetings, photo-ops and a press conference scheduled with Prime Minister Stephen Harper. Obama was to also meet briefly with Liberal Leader Michael Ignatieff.

Trade in a global economic downturn is a key issue, owing to the so-called "Buy American" provision in the $787 billion US economic recovery plan that Obama signed into law on Tuesday. The provision requires that only U.S.-made iron, steel and manufactured goods be used for public works projects receiving money from the package.

U.S. trading partners around the world demanded the clause be withdrawn over fears it could hamper an economic recovery.

During an interview earlier this week, Obama said to CBC chief correspondent Peter Mansbridge that he didn't think Canadians should be too concerned about the provision.

"My administration is committed to making sure that even as we take steps to strengthen the U.S. economy, that we are doing so in a way that actually over time will enhance the ability of trading partners, like Canada, to work within our boundaries," he said.

"And my expectation is, is that where you have strong U.S. competitors who can sell products and services, that a lot of governors and mayors are going to want to try to find U.S. equipment or services, but that we are going to abide by our World Trade Organization and NAFTA obligations just as we always have."

Speaking to CNN on the day before Obama's visit, Prime Minister Stephen Harper said protectionism presents a huge risk to the world right now.

"There is one thing that could turn a recession into a depression — it is protectionist measures across the world."

Obama has tried to downplay earlier suggestions that the U.S. could opt out of NAFTA if couldn't renegotiate the deal.

"As I've said before, NAFTA, the basic framework of the agreement, has environmental and labour protections as side agreements. My argument has always been that we might as well incorporate them into the full agreement so that they're fully enforceable," Obama told Mansbridge.

Obama added that with about $1.5 billion in trade flowing across the Canada-U.S. border daily, it is not in anybody's interest to see trade diminished.

Energy, and Canada's huge oilsands resources, are also expected to be a topic of discuss for Obama and Harper. The two leaders are expected to announce an agreement that would serve as a preliminary step to a continental cap-and-trade system.

On Wednesday morning, activists from Greenpeace Canada hung a banner from an Ottawa bridge that read "Climate Leaders Don't Buy Tarsands."

"What we're here today for is to urge President Obama to say no to the tarsands," said Mike Hudema, a campaigner with Greenpeace. "[They're] one of the dirtiest and most energy-intensive sources of oil on the face of the planet."

The banner was removed later on Wednesday by Greenpeace.