Iran’s Foreign Minister Mohammad Javad Zarif warned on Friday that any non-Iranian military forces in the Persian Gulf will be seen as a “source of insecurity.”

“Persian Gulf is vital lifeline and thus nat’l security priority for Iran, which has long ensured maritime security. Mindful of this reality, any extra-regional presence is by definition source of insecurity despite propaganda. Iran won’t hesitate to safeguard its security,” tweeted Zarif, who was sanctioned by the United States last month.

Zarif’s warning comes as the United Kingdom announced on Monday that it was going to be part of the U.S. maritime initiative in the Gulf, following the regime’s seizure of two U.K.-owned ships amid increased tensions between Iran and the United States since the latter withdrew in May 2018 from the 2015 Iran nuclear deal, reimposing sanctions lifted under it alongside enacting new financial penalties against the regime.

In response to a report that French President Emmanuel Macron invited Iranian President Hassan Rouhani to the annual G7 summit later this month to meet with the president of the United States, U.S. President Donald Trump said on Thursday that “nobody speaks for the United States but the United States itself” when it comes to dealing with Iran.

“Iran is in serious financial trouble. They want desperately to talk to the U.S., but are given mixed signals from all of those purporting to represent us, including President Macron of France,” tweeted Trump. “I know Emmanuel means well, as do all others, but nobody speaks for the United States but the United States itself. No one is authorized in any way, shape, or form, to represent us!”