The leaders of the United States, Mexico, and Canada pledged on Monday to combat the spread of the H1N1 swine flu and address climate change at their summit, but they disagreed on trade issues. US President Barack Obama, Mexican President Felipe Calderon, and Canadian Prime Minister Stephen Harper met amidst economic challenges in their countries, with a US recovery seen as crucial for regional progress. Obama and Harper announced plans to share information in anticipation of a potential increase in the H1N1 virus in the coming months. Calderon stated that the three countries are preparing to responsibly handle the return of H1N1 and minimize its impact on their populations. All three leaders pledged to uphold the North American Free Trade Agreement that connects their nations through trade, although they had differing opinions on certain issues. Harper brought up Canada's concerns with Obama regarding the "Buy American" clauses in the U.S. economic stimulus plan, which Canada worries could exclude Canadian companies. Canada is the largest trading partner of the United States. Obama emphasized the importance of considering that no extensive protectionist measures have been implemented and that the "Buy American" clauses only apply to the stimulus package and have not jeopardized the billions of dollars in trade between the two countries. Calderon, who is working to convince Obama to resolve a dispute over cross-border trucking to allow Mexican trucks into the U.S., 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 related to 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, expressing the need for urgent action on the issue before the global summit in Copenhagen in November.