"HIMARS have arrived to Ukraine. Thank you to my colleague and friend @SecDef Lloyd J. Austin III for these powerful tools," Reznikov tweeted.
The HIMARS is a Multiple Launch Rocket System developed for the US Army in the 1970s. It carries a preloaded pod of six 227mm guided missiles, or one pod loaded with a tactical missile.
Both Russia and Ukraine already operate MLRS systems but the six-rocket HIMARS version being sent to help Kyiv is more advanced, with superior range and precision.
Separately, Germany will send three such systems to Ukraine, German Defense Minister Christine Lambrecht said Wednesday.