Iran and six world powers including the U.S. are expected to miss a self-imposed deadline of today for reaching a nuclear deal in the latest round of talks. A long-term agreement would allow Iranian uranium enrichment and relief from crippling U.S.-led sanctions in return for extensive international inspections. But the U.S. has already floated the idea of extending the talks with the two sides still far apart. Key issues include the parameters for Iran’s enrichment program, the timetable for easing sanctions, and how long the deal would last. The extended talks are expected to resume next month in Oman.