Iranian Supreme Leader Ayatollah Ali Khamenei says Tehran will retaliate over the seizure of an Iranian tanker by British authorities.
In a speech on July 16, Khamenei blasted the seizure of the ship as "piracy."
"The Islamic republic and its committed forces will not leave this evil without a response," Iranian media quoted Khamenei as saying.
The Iranian supertanker was seized with the help of British Royal Marines earlier this month off Gibraltar over suspicions it was breaking sanctions by taking oil to Syria.
British Foreign Secretary Jeremy Hunt said over the weekend that Britain would "facilitate the release" of the tanker if Tehran provided guarantees the vessel would not travel on to Syria in violation of European Union sanctions.
Khamenei also said that Iran would continue to reduce its commitments under the 2015 nuclear deal, which the United States exited last year while reimposing crippling economic sanctions.
Tehran has recently taken steps to enrich uranium above the limits set by the deal to pressure European countries to help the country bypass U.S. sanctions.
Khamenei accused Europeans partners in the deal of not fulfilling their obligations.
"According to our foreign minister, Europe made 11 commitments, none of which they abided by. We abided by our commitments and even beyond them. Now that we've begun to reduce our commitments, they oppose it. How insolent! You didn't abide by your commitments!" Khamenei said.
Europeans countries have called on Iran to remain committed to the accord and reverse recent steps it has taken to reduce its commitments.