The head of the Iranian Revolutionary Guards navy Alireza Tangsiri said to ILNA news agency that the presence of America and Britain in the Persian Gulf region brings insecurity.
Answering to question about US threat of seizure of the Grace 1 has any practical effect, he said "The US has no such authority, and the seizure of Grace 1 was illegal."
He refers to seizure of a British oil tanker, the Stena Impero last month by Iran's Revolutionary Guards (IRGC), adding "Violations of this vessel have been identified and we have decided to seize it after the judiciary detects it.
Tensions have spiked between Iran and the U.S. and Britain in the Persian Gulf after the Islamic Republic shot down an American drone in June and seized a British tanker last month for violating maritime regulations.
Iran can provide security in the Persian Gulf by forming a coalition with other countries in the region, Tangsiri said.
Gibraltar officials had said this week that the U.S. Department of Justice had applied to seize the Grace 1.
While the U.S. announced it obtained the warrant to seize the tanker, Gibraltar court officials said they had not received any claim by the end of the business day, and it was not clear whether the U.S. had forwarded it, the Associated Press reported.
Iranian ambassador to London, Hamid Baeidinejad wrote on Twitter that the act of having the Iranian oil tanker, Grace 1, renamed is in no relation with skirting the US sanctions, since the tanker is not sanctioned and sails under the aegis of National Iranian Oil Company (NIOC).