Iran's Revolutionary Guards on Thursday warned against any crossings of the Strait of Hormuz without authorisation, saying vessels not complying "will be dealt with".
The future of the strait, a vital route for energy shipments that was locked down by Iran during the war, is a key sticking point in negotiations between Tehran and Washington.
Tehran has said it plans to impose what it calls maritime service fees, as opposed to tolls, while the United States argues it is an international waterway and therefore should not be charged.
"The only authorised route for passage through the Strait of Hormuz is the route announced by the Islamic Republic of Iran," said the Revolutionary Guards, the ideological arm of Iran's military.
Any crossing without authorisation is "unacceptable and extremely dangerous", they warned in a statement.
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