March 31 (Bloomberg) -- President George W. Bush urged Canada and Mexico to join the U.S. in adopting stronger border security measures that don't impede the flow of some $800 billion in trade in North America.

``We've got to make sure we work hard to secure the borders,'' Bush said at the close of a two-day summit with the leaders of Mexico and Canada.

``The whole vision of our borders is to enhance trade and tourism but prevent smugglers and terrorists and dope runners from polluting our countries,'' Bush said. ``I'm confident that with the use of technology and close collaboration we can achieve these objectives.''

Bush used the summit to tend to frayed relations with the U.S.'s two biggest trading partners. The goal of the meetings was to affirm support for free trade and address the contentious issue of immigration.

``We have to make borders much more modern with technology,'' Fox said at the closing press conference.

Bush is playing up border security as lawmakers in his Republican Party stress the issue before the November congressional elections. Republicans are divided over legislation being debated this week and next in the U.S. Senate that would overhaul immigration laws.

In response to a question, Bush refused to say whether he would veto legislation that doesn't include the guest worker program he supports. ``I want a comprehensive bill,'' he said.

One proposal in the Senate would let some undocumented immigrants stay in the U.S. while applying for legal status. House Republicans didn't offer any path to legal status for undocumented immigrants, and instead approved legislation that would increase penalties for them while building 700 miles of barriers along the 2,000-mile-long border with Mexico.

Plan Worries Canada

About 12 million people live in the U.S. illegally, and about 7.2 million of those are employed, accounting for about 5 percent of the U.S. labor force, the Pew Hispanic Center, a Washington-based research organization, reported this month.

The immigration debate, which includes increasing security on U.S. borders, also affects Canada. Canadian officials have expressed concern that a U.S. plan to require special identification cards for people who regularly cross the border would slow tourist and commercial traffic.

Canada on Border

Harper said while he understood U.S. security aims, he was worried about the possible effect on trade and the broader relationship between the countries. Canada's public safety minister, Stockwell Day, and U.S. Homeland Security Secretary Michael Chertoff will meet soon on the matter as a ``priority,'' Harper said.

The U.S. and Canada also are at odds over the $4.5 billion in duties the U.S. has levied on Canadian softwood lumber. Canada's government argues the duties violate the North American Free Trade Agreement.

Fox said the three leaders should seek to ``strengthen and maintain'' their Nafta ties. ``We are not renegotiating what has been successful,'' he said. That means going beyond the agreement to achieve such things as common standards, including the flow of people and goods through borders, Fox said.

To generate ideas on how to strengthen North American competitiveness and ease the flow of commerce across borders, Bush, Fox and Harper met immediately before the news conference with the chief executives of major corporations.

Those executives included David O'Reilly, chairman of Chevron Corp., the second-largest U.S. oil company; Robert Stevens, chairman of Lockheed Martin Corp., the world's largest defense contractor; and Michael Haverty, chairman of Kansas City Southern, the U.S. railroad that bought Mexico's biggest railroad in April.

To contact the reporters on this story: Brendan Murray in Cancun at brmurray@bloomberg.net; Holly Rosenkrantz in Cancun at hrosenkrantz@bloomberg.net

Last Updated: March 31, 2006 12:31 EST