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,

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

The assessment came as experts are trying to determine how long it would take Iran to rebuild its nuclear program in the aftermath of U.S. and Israeli strikes.