AP EXPLAINS: Iran's nuclear program as 2015 deal unravels

Iran announced Sunday it will raise its enrichment of uranium, breaking another limit of its faltering 2015 nuclear deal with world powers and further heightening tensions between Tehran and the U.S. Iran made the decision a year after President Donald Trump unilaterally withdrew from the deal. Iran has repeatedly warned Europe in recent weeks that it would begin walking away from an accord neutered by a maximalist American campaign of sanctions that blocked Tehran's oil sales abroad and targeted its top officials.