Iran, which denies seeking to develop a nuclear weapon, has insisted it will not give up domestic uranium enrichment despite the bombings of three nuclear sites. Trump told reporters that Iran has been sending out "nasty signals" and any effort to restart its nuclear program will be immediately quashed.

Iranian and European delegations will gather in Istanbul, Turkey, on Friday for fresh talks on Tehran's nuclear program.

European and Iranian diplomats have arrived in Istanbul in a renewed effort to resolve the standoff over Tehran's nuclear program. The talks mark the first formal engagement since June's 12-day war between Iran and Israel, a conflict that included U.S. airstrikes on Iranian nuclear facilities and heightened tensions across the region.