VIENNA—Iran and global powers resumed talks on April 15 to rescue the 2015 nuclear deal in an effort potentially complicated by Tehran’s decision to ramp up uranium enrichment and what it called Israeli sabotage at a nuclear site. Casting a shadow over the Vienna talks, Tehran on April 13 announced its decision to enrich uranium at 60 percent purity, a step closer to the 90 percent that is weapons-grade material, in response to an explosion at its key Natanz facility on April 11. Calling the move “provocative,” the United States and the European parties to the deal warned that Tehran’s enrichment move was contrary to efforts to revive the accord abandoned by Washington three years ago. The 2015 agreement sought to make it harder for Iran to develop an atomic bomb in return for lifting sanctions. Tehran’s refusal to hold direct talks with the United States forced European intermediaries to …