Iran's borders "represent our red line," the head of the country's powerful Revolutionary Guard warned after Tehran said it shot down a US drone over its waters on Thursday.
Tehran's response to the drone was "a clear message" from the "defenders of the borders" of Iran, said Hossein Salami, quoted by Tasnim news agency.
Iran will "respond to all foreign aggression and our reaction is, and will be, categorical and absolute."
Salami's comments come hours after the Revolutionary Guard said it shot down a US-made surveillance drone in Iranian airspace near the Strait of Hormuz, just a week after attacks on two tankers in the strategic waterway.
"The borders represent our red line," said Salami.
"We declare that we are not looking for war but we are ready to respond to any declaration of war," he added.
The United States has blamed Iran for last week's tanker attacks in the Gulf of Oman, a charge vehemently denied by the Islamic republic.
Agence France-Presse