The president's stand came on the opening day of his annual summit with the leaders of both neighboring countries. Canadian Prime Minister Stephen Harper told Bush that the passport requirement will hurt cross-border commerce and cripple tourism.

“We are committed to implementing it in a reasonable way,” said Dan Fisk, senior director for western hemisphere affairs for the U.S. National Security Council.

Concern over commerce makes the stakes of this dispute particularly high – the White House says daily trade across U.S. borders is $2.4 billion, $1.4 billion of that with Canada and $1 billion with Mexico.

Congress wants to delay the passport policy until mid-2009, but the Department of Homeland Security has not backed that idea.

Fisk did not say whether Mexican President Felipe Calderón raised the issue in his separate meeting with Bush, during which the U.S. leader praised Calderón's “courage” in taking on the drug trade. Bush and Calderón discussed both immigration and an ambitious U.S. aid plan that would have the two countries working much more cooperatively against drug trafficking.

But that plan is not yet ready to be announced, Fisk said, though the talks here will provide “more momentum and move this process along.”

He said Bush and Calderón agreed to forge “a common strategy” to fight the drug trade. However, the president stressed “that this is not a United States strategy that somehow is being given to Mexico,” Fisk said.

The Bush-Calderón agenda was made even more crowded by a powerful storm 1,800 miles away. With Hurricane Dean bearing down on the Yucatan Peninsula, the Mexican president announced late yesterday that he was cutting short the summit and planned to return to Mexico today.

He will go home bearing promises from Bush that there will be U.S. aid and help if needed to recover from the storm.

Bush interrupted his vacation in Crawford, Texas, to join Calderón and Harper at the meeting, the third of what has come to be known as the “Three Amigos” summits. Unlike earlier talks in Waco and Cancun, though, this one drew thousands of protesters, professing unhappiness with U.S. war policies and concern that closer cooperation will lead to a blurring of national identities and greater dominance by Washington.

The protesters were kept far away from Montebello, the historic chateau overlooking the Ottawa River where the leaders are meeting. The resort in the Laurentian Mountains halfway between Ottawa and Montreal features what Canadians boast is the largest building in the world made out of logs.

Another matter discussed yesterday concerned Canada's claim to sovereignty over the Northwest Passage, the famed waterway through the Arctic Ocean. Bush “came away with a far better understanding of Canada's position,” Fisk said. “However, we continue to believe that the Northwest Passage is an international waterway.”