President Barack Obama will travel to Mexico on Sunday to attend his first summit with his Canadian and Mexican counterparts, in a meeting that the latter hope will shed light on how the U.S. plans to address trade disputes involving Mexican trucks and "Buy American" provisions seen as favoring U.S. companies.

Obama, Mexican President Felipe Calderón and Canadian Prime Minister Stephen Harper are slated to touch on a wide range of topics in the two-day North American Leaders' Summit, including economic, energy, climate and security issues.

Canadian and Mexican officials said their countries will focus on trade, with Harper and Calderón closely gauging Obama's response to disagreements over "Buy America" provisions in the U.S. economic-stimulus plan, and Washington's ban on Mexican trucks operating in the U.S.

The officials said Obama's positions on those issues could serve as a bellwether of the president's broader attitude toward Canada and Mexico, the U.S.'s first- and third-largest trading partners.

Under the North American Free Trade Agreement, the U.S. is required to allow Mexican trucks to cross the border into the U.S., but U.S. trucking companies and other critics have opposed such a move, arguing Mexican trucks aren't safe. A pilot program allowed a small number of Mexican trucks to ply U.S. highways, but Congress killed that program in March following lobbying by the Teamsters Union, which represents U.S. trucking companies, among others.

Mexico retaliated by slapping an estimated $2.4 billion in tariffs on 89 industrial and agricultural products, ranging from potatoes and pears to precious-metals jewelry. Mexican truckers are also suing the U.S. under the NAFTA trade deal for $6 billion in compensation.

Click here to continue reading at the Wall Street Journal.