In a post on X, Bessent said Washington will "be shutting down both Iranian airlines' access to landing spots, refueling, and ticket sales," without providing further details.

"Only a satisfactory outcome in negotiations will end the downward spiral," he warned.

Bessent did not specify which airlines he was referring to, although Tehran's flag carrier Iran Air has previously been designated by the US State Department, while Iran's Mahan Air has also been targeted by sanctions.

But he told a press briefing later Thursday, that the United States was not going to "restrict movement for religious reasons, so Iranians who want to make the pilgrimage to Mecca or Medina will be allowed."

"We will also allow valid humanitarian reasons," he said.

His latest statement came after the Treasury on Wednesday unveiled sanctions on Iran's "Persian Gulf Strait Authority," Tehran's new agency that collects fees for traveling through the Strait of Hormuz.

Tehran has effectively closed the waterway, a key path of energy transit, after US-Israeli strikes on Iran from February 28. Energy costs have soared since.

US and Iranian forces have observed a ceasefire since April 8 while diplomats push for a negotiated settlement, but the United States and Iran traded strikes on Thursday.