Another US ship was attacked by Iraqi Exocet missiles beyond visual range on the same region just one year before. US had also attacked Iran assets in the year before after one US ship was damaged by Iranian mines. Tensions were very high.
Wasn't this in Iranian territorial waters. I don't quite see how that held up as a justification for the retaliations.
In case anyone is curious, the topic of discussion appears to be https://en.wikipedia.org/wiki/USS_Samuel_B._Roberts_(FFG-58)...
All sources appear to indicate that the mine was in international waters.