The report noted that Johnson had been in weeks-long talks with US allies France, Britain and Germany in an effort to save the JCPOA governing Iran’s nuclear program.
Although Johnson gave no reason for his departure, he did underscore that the JCPOA had been successful in curbing Iran’s nuclear program, the report said citing his farewell email to colleagues.
Trump announced on Tuesday that the United States would withdraw from the JCPOA. The president also vowed to reimpose the highest level of economic sanctions against Iran in response to Tehran's development of its nuclear program.