Which country has officially withdrawn from Intermediate-Range Nuclear Forces Treaty (INF)?

The United States has officially withdrawn from Intermediate-Range Nuclear Forces (INF) Treaty with Russia. The INF Treaty is a Cold War-era missile treaty that was signed by then US President Ronald Reagan and Soviet leader Mikhail Gorbachev in 1987. The treaty banned both countries from deploying land-launched cruise missiles in the 500- to 5,500-km range. It was a key to ending the arms race between the (then) two super powers and helped protect the U.S.'s NATO allies in Europe from Soviet missile attacks. The reasons for withdrawal are as follows: the Trump and Obama administrations have repeatedly alleged that Russia was violating the treaty by fielding a ground-based cruise missile - the Novator 9M729 ("SSC-8" in NATO terminology) that could strike Europe at a short notice, an allegation that Russia has repeatedly denied.