President Donald Trump warned Iran that the US could launch heavy strikes against the country if construction continues at Pickaxe Mountain, a suspected underground nuclear site where satellite imagery has shown increased activity this year. 

“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,” President Trump said in a speech at the midterm Republican convention. 

Pickaxe Mountain, roughly 140 miles south of Tehran near the Natanz nuclear complex, has been under construction for years. An analysis of six years of satellite imagery by the Center for Strategic International Studies found “a clear surge in construction activity” at the site this year, CNN reported. 

The center said the deeply buried facility could potentially serve as a centrifuge assembly facility, an enrichment plant, or a protected underground shelter. 

President Trump issued the warning as fighting between Iran and the US has resumed and oil prices have again climbed above $100 a barrel ahead of the US midterm elections. 

The Wall Street Journal reported that President Trump’s advisers have warned him the conflict could last through the remainder of his presidential term and potentially continue beyond it. Senior US officials, including Vice President JD Vance and Secretary of State Marco Rubio, have discussed that possibility with Trump in multiple conversations, the newspaper reported. 

In recent weeks, President Trump has moved away from pursuing an extensive military campaign against Iran, favoring economic sanctions intended to put financial pressure on the Iranian regime.