Prime Minister Stephen Harper says he will press the U.S. government on the so-called "Buy American" clause when he visits Washington this week, including a provision that has wreaked havoc on Canadian NHL teams.

Canada's six NHL teams have been scrambling to find alternative travel routes since it was announced that the U.S. Department of Transportation was banning Canadian charter planes from flying between two U.S. cities.

"This is a serious problem," Harper told Â鶹´«Ã½ Channel's Power Play in an exclusive interview. "This is another protectionist measure . . . and this situation will not be allowed to continue. I've been very clear."

"If Canadian companies can not do charter service in the United States, Americans will not be doing it in Canada," he added.

Harper will have an hour-long meeting with U.S. President Barack Obama at the White House on Wednesday.

The economy and energy are expected to be at the top of the agenda.

On Thursday, Harper will meet with congressional leaders, including Democrats Nancy Pelosi and Harry Reid. Congress has traditionally been much more protectionist than the executive office, and Harper needs to make his case on the "Buy American" provisions there.

"When it comes to issues of trade and protectionism, often our being challenges are in Congress," Harper said. "It's critical that we resist forces of protectionism."

The prime minister said that the Obama administration has been "quite positive" in regards to Canadian overtures on the "Buy American" issue.

"But it may be a case that the (Obama) administration alone can't deal with it," Harper said.

About US$280 billion of American stimulus contracts from local and state governments for infrastructure projects cannot be given to Canadian businesses.

International Trade Minister Stockwell Day has sent the U.S. government a proposal that would exempt Canada from the provision and the issue is under negotiation.

Harper also commented on Afghanistan and praised Obama's reengagement in that country.

"They are putting an enormous amount of resources and troops into that theatre ... and frankly, they are putting a lot of them where we are, in Kandahar, in a way that is very helpful," Harper said. "We are very appreciative of that."