Russia has been secretly helping Iran develop advanced supersonic cruise missiles in one of the most significant known transfers of strategic military technology from Moscow to Tehran, leaked documents show.
The multiyear covert programme, code-named C430L, has enlisted some of Russia’s most experienced missile specialists to help Iran develop a new class of weapon capable of threatening US aircraft carriers and other warships in the Middle East.
The programme, which began in 2023 and continued into the US-Israeli war against Iran, through leaked Russian correspondence, travel records and analysis of military patents.
The main purpose of C430L is to help Iran to develop a ramjet propulsion system, an engine that allows a cruise missile to sustain flight at several times the speed of sound. Missile and military experts said the technology was almost certainly intended for anti-ship and land-attack cruise missiles.
“This is the transfer of a highly strategically sensitive military technology from Russia that the Iranians have wanted to acquire for decades,” said Fabian Hinz, an expert on Iranian missiles and senior analyst with Conflict Armament Research, a UK-based weapons-tracing organisation.
“A programme like this would require political clearance from the very top in Russia.”
Supersonic cruise missiles combine speed with the ability to fly at low altitude, shortening the time available for sophisticated air and missile defences to detect and engage them. That is especially relevant for Iran in the Gulf, where the US and its regional allies operate advanced land- and sea-based defensive systems.
Iran has built and flight-tested the ramjet propulsion system, although there is no evidence that a Russian-assisted supersonic cruise missile has yet been deployed.
“For the Iranians, this would give them a qualitatively new strategic weapon system that could threaten US Navy vessels,” said Jim Lamson, a former Iran-focused military analyst with the CIA now at the James Martin Center for Nonproliferation Studies.
The leaked correspondence shows that talks over the programme continued into this summer.
It is part of the increasingly close strategic military relationship between Russia and Iran. Tehran supplied Moscow with Shahed attack drones that became an important part of Russia’s war in Ukraine, and helped Moscow establish their production inside Russia.
Ukraine and western officials have also accused Russia of providing Iran with battlefield assistance during its war with the US and Israel, including satellite imagery, drone support and weapons components.
The C430L programme represents a deeper form of co-operation, with Moscow helping Tehran acquire the know-how to develop an advanced strategic weapon system of its own.
The secret ramjet programme “shows Russia is trying to broaden the Ukraine war and draw the US into different theatres”, said Nicole Grajewski, a professor at Sciences Po University in Paris. “Russia doesn’t care as much about the red lines in the region.”
The supersonic missile assistance programme was arranged by Rosoboronexport, Russia’s state arms exporter, which co-ordinated the project with NPO Mashinostroyenia.
The US sanctioned NPO Mashinostroyenia in 2014, describing it as a significant Russian rocketry company responsible for cruise missile systems launched from ships, submarines and ground platforms, as well as work supporting Russia’s strategic nuclear forces, including intercontinental ballistic missiles.
Leaked travel records show Russian arms export officials and several senior NPO Mashinostroyenia engineers made repeated trips to Iran before the C430L contract was formally signed with Iran’s ministry of defence and Armed Forces Logistics in November 2023.
By 2025, NPO Mashinostroyenia had received a large cache of Iranian technical material relating to the ramjet propulsion system. Russian engineers then analysed data from an Iranian flight test and sent Tehran a detailed set of questions about how the system had performed.
They asked about changes to its fuel system, combustion stability, air intake and engine nozzle. The engineers also wanted to know whether the ramjet had continued operating after the telemetry supplied by Iran – data showing how the engine was performing in flight – ended less than a minute into the test.
The exchange shows NPO engineers working through the performance of a system Iran had already built and tested, using Russian experience to identify problems and help improve the design.
In April 2025, Rosoboronexport proposed sending a delegation of about two dozen Russian specialists to Iran for technical consultations under C430L. The same correspondence asked Tehran to answer the engineers’ questions about the flight-test telemetry before the proposed trip, linking the mission to the technical analysis of Iran’s propulsion system.
The Kremlin, Rosoboronexport and NPO Mashinostroyenia did not respond to requests for comment. The Iranian government, contacted through its London embassy, did not respond to questions.
Vladimir Putin, Russia’s president, told his Iranian counterpart Masoud Pezeshkian on Tuesday that Moscow was “trying to give you the help you need in this difficult period” during the war with the US and “supplying you with the goods you need”, without elaborating.
C430L was already under way when Putin in 2024 threatened to retaliate against western transfers of advanced long-range missiles to Ukraine by “supplying our weapons of the same class into regions of the world where strikes will be carried out on sensitive sites of those countries who are doing the same to Russia”.
The C430L programme forms part of a wider pattern of covert technological assistance that Iran sought from Russia and China as it strengthened its military capabilities in recent years.
The Financial Times revealed earlier this year that Moscow had agreed to supply Tehran with “Verba” man-portable air-defence systems, while the Islamic Revolutionary Guard Corps secretly acquired a high-resolution Chinese satellite that it later used to surveil US military bases across the Middle East around the time of Iranian retaliatory missile and drone attacks this year.
The US subsequently sanctioned the Chinese supplier, Earth Eye, saying it had provided satellite imagery to Iran during the war and that such imagery enabled Iranian military strikes against US forces.
Together, the programmes show how Tehran drew on Russian and Chinese technology to address weaknesses across its military, from air defence and battlefield intelligence to the development of more advanced strike weapons.
During the war, which the US and Israel launched in February, Iran has used drones and precision missile strikes to inflict significant damage on American military bases and other fixed targets across the Middle East, but has so far failed to inflict comparable damage on US naval assets.
C430L drew on some of NPO Mashinostroyenia’s most senior missile engineers, several of whom travelled repeatedly to Iran in the build-up to the signing of the contract in late 2023.
These included Alexander Dergachev, then deputy head of the defence manufacturer, who is its chief designer for sea-launched missiles and cruise missile complexes, according to leaked Russian employment records.
Alexander Chebakov, head of NPO Mashinostroyenia’s design department for air-breathing propulsion units – engines that draw in air from the atmosphere to generate thrust – also visited Tehran three times in 2023.
Russian patents reviewed by the FT show that Chebakov is a specialist in supersonic ramjet propulsion for cruise missiles. He was named as an inventor on patents covering control of supersonic ramjet engines and control of a cruise missile’s ramjet engine, among other things.
Another senior NPO Mashinostroyenia specialist selected for the proposed delegation, Yuri Prokhorchuk, worked on high-speed missile systems.
Prokhorchuk, who Russian records show is the head of the missile designer’s aerodynamics and ballistics department, was also named as an inventor on a separate NPO patent for a ramjet-powered hypersonic cruise missile designed to strike ships and land targets.
The engineers were joined on their third trip in July 2023 by Vladislav Kuzmichev, head of Rosoboronexport’s department of defence technologies and space. Kuzmichev later negotiated the contract on behalf of the state-run company with Iran’s Ministry of Defence and Armed Forces Logistics, according to documents.
Dergachev, Chebakov, Prokhorchuk and Kuzmichev did not respond to questions.
Iran has developed increasingly sophisticated ballistic missiles, including weapons it describes as hypersonic, and has a domestic industry producing turbojet and turbofan engines for slower cruise missiles.
But mastering a supersonic, air-breathing cruise missile using ramjet propulsion, which allows for sustained powered flight through the atmosphere at several times the speed of sound, has remained a significant technological gap in its arsenal.
Tehran’s attempts to close that gap – through domestic military engineering, illicit foreign procurement and efforts to reverse-engineer foreign systems – stretch back decades and have been co-ordinated at the highest levels.
In 2016, Iran’s then defence minister said the country would develop supersonic anti-ship missiles. Two years later, two Iranian diplomats were arrested in Ukraine while trying to procure parts and documentation for the Soviet-era Kh-31A supersonic anti-ship missile.
In 2019, an Iranian defence-linked company showed the then supreme leader Ayatollah Ali Khamenei inspecting a locally developed ramjet engine and, in August 2023, the IRGC-linked Tasnim news agency claimed Iran had begun testing a prototype of a supersonic cruise missile.
Hinz said developing a functioning ramjet-based weapon was extremely difficult, noting that only a small number of countries possessed the technical knowledge to do so.
“The Russians have focused on this technology for a very long time,” Hinz said. “People often think about technology transfers as being solely about sending blueprints, parts or entire missiles, but getting a 60-year-old engineer to fly over and problem-solve, using their experience, is hugely valuable.”
For Iran, mastering the engine could eventually allow it to design different weapons around the technology, improve later generations and reduce its reliance on foreign suppliers.
“If the Russians are able to help the Iranians fix their technical problems, I think this would be one of the more impactful areas of Russian military-technical assistance to Iran in recent years and one with long-term benefits for Iran’s defence industry,” said Lamson.
The correspondence shows C430L continuing into 2026, after the start of the US-Israeli war against Iran, with Russia preparing technical reports for Tehran and the two sides discussing a next phase of the development programme.
A June 2026 Rosoboronexport letter shows they were still negotiating elements of the next phase and planning further discussions over Russian technical reports. It is not clear whether the next phase of the programme has begun.
– Copyright The Financial Times Limited 2026