Russia has been helping Iran develop supersonic cruise missiles, an advanced weapon that is harder to defend against than subsonic variants, the Financial Times reported Tuesday.

According to the newspaper, the development program began in 2023 and, if successful, would give Tehran a significantly greater ability to attack US aircraft carriers and other vessels in the Middle East.

The FT said its investigation was based on Russian correspondence, travel records and military patents, and described the program as “one of the most significant known transfers of strategic military technology from Moscow to Tehran.”

The project, codenamed “C430L,” was organized by Rosoboronexport, Russia’s state arms exporter, and also involved NPO Mashinostroyenia, a rocket design organization that is under US sanctions.

Documents show that officials from both organizations traveled multiple times to Iran before the C430L project was formalized in November 2023, the FT reported.