Protectionism is the biggest threat to the global economy, Canadian Prime Minister Stephen Harper told FOX News on Friday, adding that the fifth Summit of the Americas should focus on free trade, not a potential thaw in relations between the United States and the communist island nation of Cuba.

Canada is "obviously worried about" moves to erect trade barriers worldwide, Harper told FOX News.

"The biggest threat to the economy right now is an increase in protectionism. Governments are doing all kinds of things to mitigate the effects," he said. Increased protectionism would mean "recession or worse for a very long time."

Canada, the top U.S. trading partner, recently implemented free trade pacts with Costa Rica and Chile and Harper-negotiated deals with Colombia and Peru are now before Parliament. In contrary moves, 17 of the G-20 nations have enacted dozens of protectionist measures since November.

The U.S. is trying to tamp down a trade war with Mexico, its third largest trading partner, sparked by a congressionally mandated ban on Mexican trucks moving goods into the the country. Mexico has slapped $2.4 billion in tariffs on U.S. goods in retaliation. The two nations could not end the impasse during President Obama's 20-hour summit in Mexico with President Felipe Calderon.

"We think it is very important, very important for the health of the hemisphere that we continue to bolster moves towards liberalized market economies and we need trade to do that," Harper told FOX News in an exclusive interview hours before the Summit of the Americas began Friday.

"Obviously we're worried about regimes that preach against trade, that preach protectionism. We're worried about the growth of that in the hemisphere. And it is important that countries and the United States, that we get out there and support governments — some of the ones I've mentioned — that are prepared to work with us on a liberalized trade agenda."

Harper demurred when asked if the U.S. should use the summit as a platform to defend free trade and announce additional moves to approve a pending free trade deal with Colombia or a possible breakthrough in trade talks with Panama.

"I'm obviously not here to tell the Obama administration how to run the policy of the United States," Harper said, before launching into a stout defense of Colombia and its democratic progress. "Colombia is a country that's made a great deal of progress on the democratic front, on the human rights front and on the economic front. And Colombia is a real friend to us in this hemisphere, and I think it's really essential that we support our friends that push forward economic relations with a friendly country in this neighborhood. I think if you don't support your friends you're going to find you don't have many friends."

The U.S. trade pact with Colombia was originally negotiated in 2006 and was re-negotiated in 2007 to address Democratic concerns in Congress about worker rights. Still, the trade pact languishes and there's been no signal from the Obama White House that it's a legislative or economic priority.

Dan Restrepo, a senior Obama adviser on Western Hemisphere affairs, said free trade with Panama and Columbia is "part of the matrix" of regional economic policies the president will outline here. He hinted at a deal with Panama may be in the offing, but the stalemate on Colombia continues.

"On Panama, we're engaged with the Panamanian government and working through some issues that remain and hope to make some progress quite soon," Restrepo told FOX News. "On Columbia, there are an outstanding set of issues. We're finding ways to engage with Colombia to work on those issues."

As for improved relations between the U.S. and Cuba, Harper said Obama had taken important steps to lift restrictions on family travel and remittances to the island and it was time for the Castro regime, led by Fidel Castro's brother, Raoul, to reciprocate. Harper said he knows leftist governments at the summit — namely Venezuela and Nicaragua — will try to push Cuba onto the summit agenda, but such moves ought to be resisted.

"I think it's important to hemispheric relations generally, but we certainly hope it doesn't dominate the summit," Harper said. "There are much more important issues to discuss than Cuban-American relations."