Iran is escalating its fight with the United Nations nuclear watchdog, accusing its inspectors of slander and presenting sloppy evidence, according to a legal brief compiled by the Islamic Republic and circulated among diplomats days before a key meeting in Vienna.

An outline by the Trump administration would allow Iran to continue enriching uranium at low levels while a broader arrangement is worked out that would block the country’s path to a nuclear weapon.

Iran’s supreme leader has criticized an initial proposal from the United States in negotiations over Tehran’s rapidly advancing nuclear program