The United States is set to reimpose sanctions on Iran starting tomorrow, August 6th, and that's already taken a toll on South Korea's trade with Iran.
Data from the Korea International Trade association show exports to Iran declined in the first half of this year by 15-point-4 percent compared to the same time last year.
Those exports from January to June were still worth over 1-point-7 billion dollars.
But they're going to decline further because secondary sanctions will apply to countries that continue to trade with Iran.
The sanctions coming back on Monday cover cars, metals and minerals.
Another big blow could come in November when sanctions are reimposed on oil.
South Korea buys a lot of crude oil from Iran -- around 3-and-a-half billion dollars' worth so far this year.
Seoul is currently asking the U.S. to for an exemption from the oil sanctions, something it was granted under the Obama administration.