Leaders of Canada, Mexico and the United States began a summit on Sunday in Mexico on trade issues and the threat of drug gangs.
Canadian Prime Minister Stephen Harper, Mexican President Felipe Calderon and US President Barack Obama are in Guadalajara. The event is known as the "Three Amigos" summit.
A cross-border trucking dispute is also expected to be discussed. Under the North American Free Trade Agreement, Mexican trucks are supposed to be allowed to cross into the United States, but US trucking companies say Mexican trucks are unsafe.
Mexico imposed tariffs of $US2.4 billion in US goods in March after a programme allowing them to operate beyond the US border zone was cancelled.
US business groups have been pressing the White House to resolve the dispute, saying the ban threatens to eliminate thousands of jobs.
Canadian officials are expected to raise concerns about "Buy American" elements of a $US787 billion economic stimulus programme.