US President Barack Obama has given "strong support" to Mexico's war on drugs cartels, at the start of a summit in Guadalajara.
At talks with Mexico's President Felipe Calderon, he also raised the issues of swine flu and a ban on Mexican lorries entering the United States.
Canadian Prime Minister Stephen Harper joined the two leaders for dinner.
On Monday, a three-way summit will be held, likely to focus on problems caused by the economic recession.
It will be President Barack Obama's first attendance at the annual meeting of North American leaders.
It has been dubbed the meeting of three amigos, but difficult issues divide the participants, says BBC Mexico correspondent Stephen Gibbs.
Mexico is currently experiencing what looks set to be its deepest recession since the 1930s.
It is concerned that recent US moves, including a ban on Mexican truckers operating in the US, suggest protectionism and could worsen its economic situation, our correspondent says.
Mr Harper is expected to press Mr Obama to revise the Buy America policy on public works, which has hit Canadian exporters hard.
Mexico is also unhappy with Canada's decision to require visas from Mexican visitors to the country.
The threat of organised crime is something which is more likely to unite the leaders, our correspondent adds.
Drug violence, an acute problem in Mexico, is showing some signs of spilling over the border into the southern US.
It also a growing problem in parts of Canada. Mexico will be pressing the US to free up more of its promised $1.4bn (£840m) in aid to combat drug trafficking.
August 10, 2009