The leaders of the United States, Mexico, and Canada pledged to combat the spread of the H1N1 swine flu and address climate change during their summit, but had differing views on trade issues. US President Barack Obama, Mexican President Felipe Calderon, and Canadian Prime Minister Stephen Harper met amid economic challenges in each country, with a US recovery being crucial for regional progress. Obama and Harper announced plans to share information to prepare for a potential increase in H1N1 cases in the upcoming months, while Calderon emphasized the importance of all three countries working together to minimize the impact of the virus on their populations. All three leaders pledged to uphold the North American Free Trade Agreement that links their nations in trade, although they had differences on certain issues. Harper brought up Canada's worries about the "Buy American" clauses in the $787 billion U.S. economic stimulus package with Obama, expressing concerns that Canadian businesses could be excluded. Canada is the largest trading partner of the United States. Obama emphasized the importance of recognizing that no broad protectionist measures have been implemented and that the "Buy American" provisions only apply to the stimulus and do not put at risk the billions of dollars in trade between the two countries. Calderon, who is pushing for a resolution to a cross-border trucking dispute to allow Mexican trucks into the United States, stated that all three leaders agree on the importance of adhering to NAFTA and addressing unresolved issues that hinder regional competitiveness. Obama informed Calderon that he was collaborating with the US Congress to address safety issues with Mexican trucks. He emphasized the importance of avoiding protectionism and instead expanding trade between the United States, Mexico, and Canada. The leaders also released a statement on their joint efforts to combat climate change in preparation for the upcoming global summit in Copenhagen. They stressed the urgency of taking aggressive action on climate change.