“We gotta erase his head from his torso,” Mr. Pearson said in an intercepted communication on the encrypted platform Sky ECC.
For reasons that are unclear, the hits were never carried out.
The men — who claimed to have organized a four-man team, including a driver — agreed to a $350,000 payment in January 2021. Mr. Zindashti, identified by the Treasury Department as a drug trafficker working at the behest of the Iranian Ministry of Intelligence and Security, sent them photographs of the targets, a man and a woman, along with maps.
He appears to have paid them only $20,000 for travel expenses, the prosecutors said.
The charges stem from a yearslong investigation by the F.B.I., the Justice Department and Royal Canadian Mounted Police.
Law enforcement officials said the investigation was continuing and did not rule out the possibility that others could be charged.
“To those in Iran who plot murders on U.S. soil and the criminal actors who work with them, let today’s charges send a clear message: The Department of Justice will pursue you as long as it takes,” Assistant Attorney General Matthew G. Olsen of the department’s national security division said in a statement.