Iran warned Israel on Monday not to cross its "red lines" in the Gulf in the final days of Donald Trump's presidency and following a reported Israeli submarine deployment.
Foreign ministry spokesman Saeed Khatibzadeh stressed the Islamic republic would defend itself against any American military "adventure" in the runup to the January 20 handover of power in Washington.
The statement came a week after the US Navy announced a nuclear submarine was being deployed to the Gulf, in a new show of force directed at Iran.
Media in Israel have since reported that an Israeli submarine has crossed the Suez Canal also headed for the Gulf, a report that has not been officially confirmed or denied.
"Everyone knows what the Persian Gulf signifies for Iran," Khatibzadeh told an online news conference.
"Everyone knows the policies (of Tehran) regarding security and national security... Everyone knows very well how high the risk is raised if the red lines of Iran are crossed."
Tehran accuses its regional foe Israel of responsibility for several anti-Iranian operations, including the assassination last month of nuclear scientist Mohsen Fakhrizadeh.
The United States, for its part, has accused Iran of involvement in a rocket attack last week near its Baghdad embassy, as Tehran prepares to mark the first anniversary of the killing of top Iranian commander Qasem Soleimani in a US drone strike in January.
"We have sent messages to the US government and our friends in the region (warning) the current US regime not to embark on a new adventure in its final days at the White House," said Khatibzadeh.
He said Iran was not seeking to increase tension and called for "rational people in Washington" to take the same line until President-elect Joe Biden replaces Trump in the White House.
Decades-old tensions between Washington and Tehran have soared since 2018, when Trump unilaterally withdrew the United States from the Iran nuclear deal.
The arch enemies have twice come to the brink of war since June 2019, especially following the killing of Soleimani.