President Donald Trump speaks at an event at the Carrier HVAC plant in Indianapolis on Dec. 1, 2016, during his election campaign.

President-elect Donald Trump is threatening heavy taxes as retribution for U.S. companies that move their business operations overseas and still try to sell their product to Americans.

In a series of early-morning tweets Sunday, Trump vowed a 35 percent tax on products sold inside the U.S. by any business that fired American workers and built a new factory or plant in another country.