Donald Trump will name Robert Lighthizer, a former trade official under President Ronald Reagan, to head the U.S. Trade Representative office . …

Mr. Trump has signaled a major shift in policy, threatening China and Mexico with tariffs if they don’t right alleged trade wrongs. That could carve out a new role for the trade office, compared with under previous presidents.

Mr. Lighthizer has three decades of experience arguing for punitive tariffs on overseas companies. Given Mr. Trump’s deep skepticism of trade agreements such as the North American Free Trade Agreement, or NAFTA, Mr. Lighthizer probably wouldn’t prioritize major new trade agreements, at least in the early days of the administration, according to people following Mr. Trump’s trade plans.