Even with a new representative of Mexico, though, the leaders are unlikely to shed the title given them at the two earlier summits – the Three Amigos. Just as hard to shake have been the issues confronting them as once again they will grapple with all the problems that arise from sharing almost 7,500 miles of border during a time of increased anxiety over terrorism.

Bush will interrupt his Texas vacation for two days of meetings in a historic log chateau overlooking the Ottawa River.

The White House has tried to elevate the summit discussions, with spokesman Gordon Johndroe last week saying that they will be talking about global issues such as Afghanistan, the Middle East, Iran, climate change and world trade.

Bush also will be meeting one on one with each of the other leaders. It is in those smaller meetings that irritants between the neighbors will come to the surface. Canada remains in a squabble with the United States over Washington's efforts to block Canadian softwood from coming into the U.S. market. Mexico is unhappy with what it views as U.S. noncompliance with the North American Free Trade Agreement when it comes to trucking and avocados.

There is a chance that Bush will be able to announce a sweeping program in which the United States would provide unprecedented aid to Mexico and would work together with Mexican officials to break the back of the illegal drug trade. But on the eve of the summit, work had not yet been completed on that and it was not ready for unveiling.

Almost certainly, both Calderón and Harper will voice their frustrations with the Bush administration's plans to require passports for anyone to cross into the United States from either neighboring country, something they see as a potentially crippling blow to commerce.

The White House has agreed to delay the passport requirement for land crossings until 2008, but both Harper and Calderón are expected to push Bush to go further to head off the anticipated increases in paperwork and lengthening of costly delays at the border.

Former U.S. Ambassador to Mexico Jeffrey Davidow said the specter of passports is having “a very chilling effect on border communities.” Davidow, president of the Institute of the Americas at the University of California San Diego, noted that delays at the San Ysidro crossing routinely exceed an hour.

“The idea that one will have to invest money and time to get a passport in order to cross over the border to see Juarez or Tijuana, to have a meal or to do some shopping or play golf, it's just going to have a very negative effect on border economies,” he said.

Both Bush and Calderón hope to highlight areas of agreement, particularly after the contentious debate in Washington over efforts to combat illegal immigration. Fox had used the Waco and Cancun summits to support Bush in his battles with Congress, but he left office without seeing any change in U.S. policy.

Now, Mexico would like to move beyond that debate.

“We need to rebalance the bilateral relationship,” Mexican Ambassador to the United States Arturo Sarukhan said in a recent speech in Washington. “In the past six or five years, immigration and immigration reform became the sole, single driver of this bilateral relationship.”

Sarukhan said it became “the horse pulling the cart of the U.S.-Mexico bilateral relationship.”

Today, he wants the focus on “other very critical issues,” leading with what he called “drugs and thugs.”

That was a reference to the drug aid, which is expected to be a multiyear, multimillion-dollar program of aid to include wiretapping equipment, aircraft, radar and joint training exercises.

The other issues cited by the ambassador were infrastructure along the border and management of scarce water resources. Sarukhan promised that Mexico would do its part.

“On many of these issues, it's been easy to wag our finger to the north when we sometimes forget that Mexico is as co-responsible as the United States in the solution to some of these challenges,” he said.

Peter Hakim, president of the Inter-American Dialogue, a Washington center that studies North American issues, said that energy would be an important part of the summit agenda as well.

“There is good reason for the three countries to cooperate on that,” Hakim said. “Both Mexico and Canada need a lot of U.S. investment if they are going to take advantage of their oil fields.”