A 25-percent U.S. tariff on imported auto parts officially took effect on Saturday.

As outlined in U.S. President Donald Trump’s March 26 proclamation, the tariff began at 12:01 a.m. Eastern Time.

It follows a similar 25-percent duty on foreign-made cars that was implemented last month.

To ease the burden on automakers with production facilities in the U.S., Trump issued a revised proclamation on April 29 that allows for partial relief over a two-year grace period.

While the changes offer some breathing room, South Korean suppliers are still expected to take a hit.

According to the Korea International Trade Association, the U.S. accounted for 36-point-5 percent of Korea’s auto parts exports last year, worth 13-point-5 billion U.S. dollars.