Washington (CNN) -- In a brief visit Wednesday to Toluca, Mexico, U.S. President Barack Obama will join his two North American counterparts to discuss environmental issues, security, driving economic growth through trade, and job creation. The North American Leaders' Summit, which has come to be known as the "Three Amigos" summit, began in 1992 with President George H.W. Bush. Obama and Canadian Prime Minister Stephen Harper will visit Mexican President Enrique Pena Nieto. Here are four issues among friends: 1. Butterflies and oil: While the Keystone XL pipeline continues to cause friction between the United States and Canada, the monarch butterfly is a sore spot in U.S.-Mexico relations.
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The North American Leaders' Summit is Wednesday in Toluca, Mexico
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U.S. and Canadian leaders will visit Mexican President Enrique Pena Nieto
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Since its beginning in 1992, it has become known as the "Three Amigos" summit
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Keystone, trade and immigration are likely to dominate the discussions
The Mexican government says the visa requirement is invasive and time-consuming, and blames it for a decline in the number of @placeholder visitors to Canada.