President Trump said Friday that there is a “good chance” that U.S. and Mexican officials could strike a deal that would remove the need to impose tariffs he has threatened, shifting his tone as the two sides continued to negotiate steps to address the surge of migrants crossing the U.S. southern border. “If we are able to make the deal with Mexico, & there is a good chance that we will, they will begin purchasing Farm & Agricultural products at very high levels, starting immediately,” Trump said in a tweet. “If we are unable to make the deal, Mexico will...