President Trump then slapped unilateral trade and financial sanctions on Iran.
The US had initially provided South Korea with a waiver to avoid implementing the new sanctions, but those lapsed, essentially forcing Seoul to freeze the Iranian assets.
Iran s move to seize the vessel also coincides with Tehran s announcement that it will increase the level of uranium enrichment at its Fordo nuclear facility to 20%, well above that agreed to with several countries, including the US, until Trump s withdrawal from the deal in 2018. Uranium enriched to 90% is required to fuel nuclear weapons. Iran claims its nuclear program is strictly for peaceful purposes.