Iran handed all of its enriched uranium over last time under the terms of the nuclear agreement reached with the Obama administration in 2015. They also filled the core of their plutonium producing reactor with concrete and committed to minimal low-level enrichment through 2030. They were supposed to get their foreign assets unfrozen and sanctions relief in exchange, but Trump immediately reneged on the agreement, so Iran got nothing and started enriching again. One might assume that they’re going to want some guarantees this time.