The UN’s nuclear watchdog agency is asking the body to hold Iran accountable for failing to stick with safeguards meant to prevent the development of nuclear weapons, diplomatic officials announced Wednesday.

It’s the latest chapter in a more than decade-long effort to keep an eye on Iran that has seen the country descend from compliance to sabotaging inspection efforts – such as disabling monitoring cameras and “excessively invasive physical searches” of inspectors – according to multiple former officials, diplomats and more than a decade of UN documents reviewed by CNN.

Iran’s 2015 nuclear deal with the US and other countries established the world’s most invasive nuclear inspection regime, overseen by the International Atomic Energy Agency. And for years, Tehran’s nuclear program complied with the agency’s inspectors.

But during the years after President Donald Trump withdrew from that deal, Iran gradually and systematically defied its nuclear safeguards, according to contemporaneous IAEA reporting, and the agency later concluded that Iran failed to disclose nuclear material-related sites.

“The Iranians were really playing rope-a-dope and consistently making it hard for the IAEA to get access, presenting information that was laughably not true or plausible,” said a former US diplomat whom CNN granted anonymity to freely discuss the sensitive topic.