KenV point taken about an overt act of war. Now assume that one of the carrier group hits a mine in "international waters" try proving that the Koreans or Iranians were responsible? If were the Iranians I would use one of their nice quiet German Submarines to go lay some mines around the straights and not tell anyone.
Has happened before, the RN had a ship hit a mine while travelling between Corfu and Albania many years back.
Corfu Channel Incident 1946, Mining of HMS Saumarez and Volage