The head of the United Nations’ nuclear watchdog agency on Monday urged that inspections not be used as a “bargaining chip” as Iran, the United States and other nations lock horns over how to revive their beleaguered nuclear deal. International Atomic Energy Agency chief Rafael Grossi appealed to all sides to engage in “constructive discussions” as the Vienna-based agency’s 35-nation board met Monday. Iran enacted a law late last month that restricted snap access for inspectors to some sites and surveillance cameras, complaining that it is not reaping the economic rewards it was promised under the 2015 deal in exchange for curbs on its nuclear program.

Without the work of inspectors, “you don’t know whether you can sleep tight or be very, very concerned at night,” Grossi said. “The inspection work of the IAEA should not be put in the middle of a negotiating table as a bargaining chip.”

Iran said Sunday that it would reject an early meeting with the United States and European signatories to the deal because of their “recent positions and actions.” However, Western officials have said that Iran’s private response has been more nuanced and that it has sought assurances that talks would be limited to the nuclear deal. “We’re disappointed in Iran’s response,” White House spokeswoman Jen Psaki said Monday.