They say Iran must abandon uranium enrichment, but this is one of our red lines. If talks are conditional on halting enrichment, they simply won’t happen," said Ali Velayati, senior adviser to Supreme

If the negotiations must be conditioned on stopping enrichment, such negotiations will not take place,' said an advisor to Iran's supreme leader on Monday. Israel and Western nations accuse Iran of pursuing nuclear weapons,

Officials in Israel are acknowledging that some enriched uranium may have survived the powerful U.S. strikes on Iranian nuclear facilities last month.