US State Department spokesman Ned Price said on Monday said a comment by Iran's Supreme Leader Ayatollah Ali Khamenei about uranium enrichment "sounds like a threat" and declined to respond to what he described as "hypotheticals" and "posturing."
Price reiterated US willingness to engage in talks with Iran about returning to the 2015 nuclear deal.
Khamenei said on Monday Iran might enrich uranium up to 60% purity if the country needed it and would never yield to US pressure over its nuclear activity.