The State Department (State) is three years late in slapping certain sanctions on Iran, prompting new allegations that the Barack Obama administration is deliberately skirting US law in its quest for a nuclear deal.

Under the Iran, North Korea and Syria Nonproliferation Act (INKSNA), State is supposed to inform Congress every six months of attempts to help the three countries obtain weapons of mass destruction and certain missile technology. The law requires the agency to sanction violators or justify its decision not to.

But the department has fallen way behind in recent years, according to a government watchdog report obtained by Al-Monitor. Delays have kept on getting longer, with Congress receiving an update on violations committed in 2011 only in December 2014.

"Our analysis demonstrates that State is falling further and further behind in providing the reports and is now juggling a backlog of draft reports at different stages of that process," the US Government Accountability Office (GAO) report concludes. "The imposition of sanctions no sooner than 3 or more years after the transfer occurred may diminish the credibility of the threatened sanction."