President Barack Obama will strive to come to an agreement with his Mexican and Canadian counterparts on the Trans-Pacific Partnership as the three leaders meet this week to discuss how the members of Nafta will fit into the new, far-reaching trade pact.

Mr. Obama, Mexican President Enrique Peña Nieto and Canadian Prime Minister Stephen Harper will tackle a wide-ranging agenda including security, energy and immigration issues when they gather Wednesday in Toluca, Mexico, for the North American Leaders' Summit. Economic competitiveness...