The United States has declared its intent to officially suspend its obligations under the 1987 US-Soviet Intermediate Nuclear Forces (INF) Treaty as of 2 February 2019, and is likely to begin a six-month notice of withdrawal period.
The announcement follows long-standing US concerns over alleged Russian treaty violations, especially involving the development and deployment of the Novator 9M729 ground-launched cruise missile (GLCM), part of the 9K720 missile system and known in US nomenclature as SSC-8.
The INF Treaty eliminated conventional and nuclear land-based ballistic and cruise missiles in the 500-5,500 km range bracket.
Two potential US responses to the INF Treaty's demise - developing a low-yield warhead for the in-service Trident D-5 submarine-launched ballistic missile (SLBM) and a future nuclear-armed sea-launched cruise missile (SLCM) - have already been detailed in the Trump Administration's Nuclear Posture Review (NPR). For example, the NPR announced that the US "will modify a small number of existing [Trident D-5] SLBM warheads to provide a low-yield option", with such an option being "important for the preservation of credible deterrence against regional aggression".
US officials have said there are no discussions underway about basing any new systems in Europe as a response, so options such as those already set out in the NPR could be part of how Washington seeks to offset any increase in Russian capability.
What is the SSC-8?
Although the 9M729/SSC-8 system's capabilities remain unconfirmed, the missile is believed to be derived from the in-service 3M-14 Kalibr SLCM and may have broadly similar capabilities.
To refute US accusations of the INF violation, Russian officials displayed the 9M729/SSC-8 system in January and said its maximum range is 480 km. The officials said the two weapons share the same engine, fuel tank and booster, but the 9M729 has a new warhead and guidance system that make it longer and heavier than its predecessor.
Andrea Thompson, US undersecretary of state for arms control and international security, noted that a static display of the system does not verify how far the missile flies and suggested that US intelligence reporting indicated it has flown farther in testing.