Trump warns Tehran over Pickaxe Mountain activity; U.S.-Iran exchange attacks on ships near Hormuz

U.S. President Donald Trump has urged Iran "not to get cute" over activity at a suspected nuclear site on Pickaxe Mountain, following a barrage of attacks between both countries on tankers around the strategically vital Strait of Hormuz.

"We notice there's a little activity at ‌Pickaxe. I would advise Iran not to get cute because we will have to hit them very hard," Trump said Wednesday at the midterm Republican convention.

Situated near Iran's heavily damaged Natanz uranium enrichment facility, Pickaxe Mountain is regarded as one of the last remaining vestiges of Tehran's nuclear program.

The U.S. president has previously threatened to attack the underground tunnel complex, which is known as Kuh-e Kolang Gaz La in Farsi, amid concerns that Iran could reconstitute its nuclear program.

An analysis of satellite imagery by the Center for Strategic and International Studies (CSIS), published Wednesday, showed more road activity at Pickaxe Mountain in 2026 "than at any point in the site's history" and "a clear surge" in construction activity.

The latest data indicates that activity at the site "has shifted from active excavation toward probable internal construction and continued exterior reinforcement," CSIS said.

The think tank, which said it could not substantiate or refute claims that Iran has moved uranium centrifuges into Pickaxe Mountain, said the flurry of activity at a site just two kilometers (1.2 miles) away from an old uranium facility at Natanz was "suspicious."

Iran has repeatedly denied it is seeking nuclear weapons.

A spokesperson at Iran's Embassy in London was not immediately available to respond to a CNBC request for comment.

U.S. forces struck three Iranian nuclear sites in June 2025, including Natanz, Fordow and Isfahan, which American officials said at the time had significantly set back the prospect of Tehran building a nuclear weapon.

Iran said Wednesday that it had fired ballistic missiles at a U.S. military base in Jordan and attacked 10 ships near the Strait of Hormuz, a narrow waterway that typically handles around 20% of the world's oil traffic.

Earlier in the week, U.S. Central Command forces said five Iranian oil tankers had been destroyed in response to the Islamic Revolutionary Guard Corps targeting a U.S. Navy warship with ballistic missiles twice in two days.

The attacks on tankers near the Strait of Hormuz, alongside an escalation in fighting between Saudi Arabia and the Iran-backed Houthis in Yemen, have put energy market participants on alert for further supply disruptions.

International benchmark Brent crude futures with November delivery traded 0.8% lower at $100.40 per barrel on Thursday morning, with U.S. West Texas Intermediate crude futures last seen down 0.6% at $95.51.

Speaking to reporters on Wednesday, Trump said he did not think the U.S.-Iran war would end until after November's midterm elections. "I think the war will end immediately after the election because they can't hold out any longer," Trump said.

The U.S. president later added that some short-term economic pain for American consumers was worth it to prevent Iran from developing nuclear weapons.