So, you know how there's always chatter about potential back-channel talks when geopolitical tensions spike? Well, Iran's top security official just poured a big bucket of cold water on that idea.

Ali Larijani, a former advisor to the late Supreme Leader Ayatollah Ali Khamenei, took to social media on Monday to set the record straight: Tehran is not looking to negotiate with the United States. In a series of posts, he stated that Iran is merely defending itself and "did not start the aggression."

But he didn't stop there. Larijani also took direct aim at former U.S. President Donald Trump, accusing him of plunging the region "into chaos with his 'delusional fantasies,' and now fears more American troop casualties." He added that Trump's actions had turned the "America First" slogan into "Israel First," arguing American soldiers had been sacrificed for "Israel's power-hungry ambitions."

It's a pretty stark rejection, and it comes at a particularly volatile moment. Just hours before Larijani's posts, Israel launched strikes on Beirut in retaliation for an attack by Hezbollah—a group backed by Iran. This followed a series of U.S. and Israeli military strikes against Iranian targets over the weekend, which saw support from allies like Canada and the UK, and calls for restraint from others.

For investors, the immediate worry isn't just the rhetoric or even the rockets; it's the oil. All this escalation is happening right next to the Strait of Hormuz, the narrow waterway through which about a fifth of the world's oil passes. Analysts are now warning that any serious disruption there could send crude prices soaring toward $100 a barrel. The risk is real enough that major energy firms and tanker operators have already started suspending shipments after Tehran issued cautionary advice to vessels in the area.

In short, the door to diplomacy appears firmly shut from Iran's side for now, and the markets are bracing for the potential fallout in the world's most important oil chokepoint.