President Donald Trump is congratulating Andres Manuel Lopez Obrador on taking office as Mexico's new president.Trump tweets that Lopez Obrador had a "tremendous political victory with the great support of the Mexican People."Trump predicts the two will "work well together for many years to come!"Lopez Obrador was sworn in to office on Saturday.Congratulations to newly inaugurated Mexican President @lopezobrador_. He had a tremendous political victory with the great support of the Mexican People. We will work well together for many years to come!— Donald J. Trump (@realDonaldTrump) December 3, 2018 More than 30 million Mexicans voted for him in a sweeping July 1 election victory.The day he was sworn in, Lopez Obrador signed an agreement with El Salvador, Guatemala and Honduras to work on a plan to stem migration to the US from those countries. The issue of Central American migrants has vexed Trump, who has complained that Mexico hasn't done enough to stop the flow.Trump has sent thousands of troops to the southern border.