Iranian security chief Ali Larijani declared in a post on X that Iran "will not negotiate" with the United States.
Larijani's comments contradict previous claims by US media that there was a new effort to restart nuclear talks with Washington.
The statement came after the Wall Street Journal alleged that Larijani had made this attempt through Omani intermediaries after Khamenei's assassination.
For his part, United States President Donald Trump has declared that the strike on Iran will continue for several weeks. Trump said that 48 Iranian leaders have been killed in US and Israeli attacks.
The White House chief of staff expressed satisfaction with the progress of the strikes so far. He also said that 9 Iranian naval vessels have been destroyed.