The international agreement on Iran’s nuclear program moved forward Monday with the first meeting of the Joint Commission responsible for monitoring how both sides implement their parts of the deal, amid some optimism that the plan could roll out by the end of the year.

Monday’s session brought high ranking officials from Iran and the group that includes the United States, Britain, China, France, Russia, Germany and the European Union back to Vienna, the city where they agreed in July to limit Iran’s nuclear program in exchange for needed sanctions relief.

It follows Sunday’s so-called Adoption Day when the sides took their first formal steps to implement the deal.