The thinner the Canada-U.S. border, the better

This country has spent years trying to diversify its trade with new partners, from South Korea to the European Union, and that is a very good thing. But basic geography means one economic and trade partnership will always dwarf all others.

Canada shares the world's longest undefended border with the world's biggest economy, and trade with the United States remains our most important relationship. It's our biggest economic opportunity when it goes smoothly, and our biggest economic frustration when it hits roadblocks, as it did after 9/11. The two countries did nearly $800-billion in trade last year, and American tourists spent more than 50 million nights in Canada.

So Prime Minister Stephen Harper and his government deserve congratulations for inking an agreement with the Americans that offers the prospect of a smoother, thinner border. Customs preclearance measures already in place at many airports could eventually cover road, rail and water transport.

As the smaller partner, Canada needs the deal more urgently than the U.S., and it may be some months or years before Congress gets around to passing the legislative changes that will put it into effect.

But this is a step forward in the historical continental relationship, and despite the reaction that is sure to follow from some Canadian nationalists, will not imperil our nation's sovereignty. (American border officials have been working at eight Canadian international airports for decades, prescreening travellers to the U.S. The sky has yet to fall.)

The deal promises to simplify and speed up the passage of people and goods across the border – which should spur the movement of more people and more goods.

Border crossings have yet to recover to the level from which they fell when the Americans tightened border procedures and travel-document requirements in the aftermath of the 9/11 attacks. For example, according to the U.S. Department of Travel Statistics, 7.1 million trucks and 90 million car passengers crossed the border in 2000. In 2014, only 5.8 million trucks and 59.6 million car passengers did.

Anything that restricts movement is bad for Canadian exporters, including Canadian companies with integrated supply chains. It's also bad for Canadian tourism. It is in Canada's interest to erase the line as much as possible.

Mr. Harper's government has rightly sought to multiply Canada's trade options beyond the U.S., but it's past time for the 2011 Beyond the Border bilateral agreement to be put into force.

Because of tensions over Keystone XL, the Canada-U.S. relationship has cooled under Mr. Harper and President Barack Obama. It's encouraging to be reminded the two countries remain very much open to each other's business.