Americans never stopped working on forbidden rockets even if they were part of the INF Treaty. They [Americans] were working on new rockets and the time to test them has come now. In order to save the face, they created this entire circus and left the [INF] Treaty.
In fact, Russia bears primary responsibility for the end of the INF Treaty, because it has produced, tested and deployed the 9M729 missile, which violates it. In July 2014 the then-US President Obama officially accused Russia of testing a missile in violation of the INF Treaty, which prohibits the US and Russia from possessing, producing or test-flying ground-launched ballistic and cruise missiles with ranges between 500 and 5500 kilometres.
The US has gathered detailed information on Russia’s flight-testing of the 9M792 missile to distances well over 500 kilometres and has spent almost six years in dialogues with Russia to try to resolve Russia’s non-compliance. However, Russia consistently refused to address US and NATO concerns.