The US State Department has labeled comments by the advisor to the Iranian Supreme Leader as "irresponsible" after he warned that Iran could change its nuclear strategy if threatened by Israel.

The US is committed to preventing Iran from developing nuclear weapons, State Department spokesman Matthew Miller said at a press briefing on Thursday.

Earlier this week, in an interview with Al Jazeera, Kamal Kharrazi, an advisor to Iran's Supreme Leader Ali Khamenei, warned that "if [Israel dares] to strike Iran's nuclear facilities, [Iran’s] level of deterrence will change."

"As the President and Secretary have made clear, the United States will ensure one way or another that Iran will never have a nuclear weapon. We continue to use a variety of weapons – or sorry – a variety of tools in pursuit of that goal and all options remain on the table," Miller said in response.

Despite the warning from Kharrazi and Iran’s repeated noncompliance on its nuclear program, Miller acknowledged that diplomacy remains the preferred route for achieving a sustainable resolution.

The spokesperson did point out that diplomatic efforts are currently hindered due to Iran's recent escalatory actions and its lack of cooperation with the International Atomic Energy Agency (IAEA).

In recent months, a number of officials close to the Supreme Leader have threatened that the Islamic Republic has the capability to build an atomic bomb.

“We have no decision to build a nuclear bomb but should Iran's existence be threatened, there will be no choice but to change our military doctrine,” Kharrazi said, who previously served as Iran’s Minister of Foreign Affairs and currently leads the Strategic Council of Foreign Relations.

The statement comes shortly after the visit of Rafael Grossi, the director-general of the UN nuclear watchdog, the IAEA, to Tehran.

Grossi reported that there was “no timeframe or deadline” for Iran to resolve its nuclear issues, but he emphasized the expectation for Iran to take swift action.