President Donald Trump concedes that some Apple products may become more expensive if his administration imposes “massive” additional tariffs on Chinese-made goods, but he says the tech company can fix the problem by moving production to the U.S.

“Start building new plants now. Exciting!” Trump said Saturday in a tweet aimed at the Cupertino, Calif.-based company.

Last week, Apple said that a proposed new round of $200 billion in additional tariffs on Chinese imports would raise prices on some of its products, including the Apple Watch and the Mac mini.

The company makes many products for the U.S. market in China, and it also sells gadgets in China.