Iran warned Monday that it would respond “ferociously” to any U.S. attack, no matter how limited, after President Donald Trump said he was weighing possible strikes against the Islamic Republic.

Washington has increased its military presence in the Middle East to pressure Tehran ahead of nuclear negotiations set to resume Thursday. Trump has signaled that a limited strike remains an option if talks fail to produce a deal.

Iran’s Foreign Ministry said any military action, even on a small scale, would be considered an act of aggression.

“And any state would react to an act of aggression as part of its inherent right of self-defense, ferociously. So that’s what we would do,” ministry spokesman Esmaeil Baghaei said at a briefing in Tehran attended by an Agence France-Presse (AFP) journalist.

The two countries concluded a second round of indirect talks in Switzerland on Tuesday under Omani mediation.