EghtesadOnline: "The implementation of the agreement is still fragile," International Atomic Energy Agency chief Yukiya Amano said in an interview with the German news agency DPA published on Friday before a trip to Germany.
"Small technical mistakes, small failures in implementation can become big political issues that could have a large negative influence on the agreement," he added.
Amano's agency has reported that Iran so far has stayed within the terms of the agreement, according to ILNA.
Iran has also complained that the United States is not keeping its side of the deal. It wants Washington to do more to encourage banks to do business with Iran. Many are wary that doing so would run afoul of U.S. sanctions still in place.
The Republican candidate for U.S. president, Donald Trump, has strongly criticized the deal, though he has also conceded that it would be hard to tear it up as he had previously said he would.
The United States says it has done everything required by the agreement, which was also signed by Russia, China, France, Britain and Germany.