Iran has allowed inspectors from the United Nations' nuclear watchdog to return, following a month-long suspension of cooperation after a conflict involving Israel and the United States. The inspectors' visit marks a potential step toward restoring oversight of Iran's nuclear program, which has raised international concerns due to its stockpile of highly enriched uranium. European governments have warned Iran that sanctions will be reinstated unless progress is made toward renegotiating limits on uranium enrichment before the 2015 agreement expires in October. Despite the resumption of inspections, diplomatic talks have yet to yield substantive changes, and the threat of renewed sanctions looms as negotiations continue.