Donald Trump announced Thursday that brand-name or patented pharmaceutical products will be subject to a 100% tariff starting October 1 – unless the drugmaker is building a manufacturing plant in the US.

Trump has been promising for months to levy tariffs on pharmaceutical imports, which avoided tariffs during his first term. The president sees tariffs as a way to pressure drug manufacturers to ramp up production in the US and to strengthen the supply chain for essential medicines.

Also, Trump has pointed to tariffs as a way to fulfill his vow to lower drug costs, though experts say that is unlikely to happen.