(FOX NEWS) — Iran has threatened to take action if President Donald Trump follows through on threats to use military force against civilian targets if Tehran fails to capitulate.

“Iran will not stand idle in the face of such egregious war crimes,” said Amir-Saeid Iravani, Iran’s permanent representative to the United Nations. “It will exercise without hesitation its inherent right of self-defense, and will take immediate and proportionate reciprocal measures.”

Iravani said Iran has rejected a temporary ceasefire proposal, “particularly in light of the June experience, when hostilities resumed under false pretext. A ceasefire in this context serve only to the arm and prepare for the continuation of further crimes.”

Trump has set an 8 p.m. EST deadline for Iran to open the waterway, or else face the destruction of its power plants and bridges.

“A whole civilization will die tonight, never to be brought back again. I don’t want that to happen, but it probably will,” Trump wrote on Truth Social on Tuesday.

A UN envoy tasked with helping resolve the Strait of Hormuz crisis is “on his way to Tehran” to continue consultations with mediators, signaling renewed diplomatic activity despite ongoing tensions, Iravani said.