TEHRAN, Iran — Iran’s atomic energy chief claimed on Thursday that the U.N. nuclear watchdog misunderstood the nature of the experiments at a Tehran laboratory mentioned in the agency’s latest report. The report underscored the West’s concerns about Iranian nuclear ambitions and came as the U.N. Security Council inches toward imposing a new round of sanctions on Tehran for refusing to suspend its nuclear enrichment. Ali Akbar Salehi said the International Atomic Energy Agency’s report earlier this week made a “misinterpretation” in a reference about pyroprocessing — a procedure that can be used to purify uranium metal used in nuclear warheads. Salehi, according to the semiofficial Isna news agency, said the Tehran lab experiments deal with uranium production, not pyroprocessing. “The experiments have no relation to pyroprocessing,” he said. “We believe the agency used this false report about a process that has not yet taken place, with the purpose of influencing public opinion.” Salehi stressed such “mistakes” would backfire and only damage IAEA’s reputation.