"It's pretty clear that this is a system that was transferred from Russia in the hands of separatists," Kerry told CNN, saying that the Buk M-1 anti-aircraft missile system had been used to hit MH17 over eastern Ukraine on Thursday.
"We know with confidence, with confidence that the Ukrainians did not have such a system anywhere near the vicinity at that point in time. So it obviously points a very clear finger at the separatists."
Kerry said the US had "extraordinary circumstantial evidence" of the incident that killed all 298 people on board the Malaysia Airlines plane from Amsterdam to Kuala Lumpur.
"We picked up the imagery of this launch. We know the trajectory," he told NBC's Meet the Press. "We know where it came from. We know the timing."
"And it was exactly at the time that this aircraft disappeared from the radar. We also know, from voice identification, that the separatists were bragging about shooting it down afterwards," he said.
Earlier, the Washington Post, quoting a US official said Russia gave at least three Buk missile launchers to Ukrainian rebels and attempts were made to move the sophisticated systems back into the country after the downing of MH17.
"We do believe they were trying to move back into Russia at least three Buk [missile launch] systems," the Post quoted a US official as saying.
US intelligence was "starting to get indications ..... a little more than a week ago," that the Russian launchers had been moved into Ukraine, the official said as the blame game continued with Russia accusing the US and the West of pointing fingers at it to push their agenda on Ukraine.
The US official's comments, made on condition of anonymity to speak about intelligence matters, came as a top Ukrainian counterintelligence official said his service has conclusive proof that Russia supplied the missile that shot down the plane over territory controlled by the separatists, the report said.
US President Barack Obama on Friday said that Russia likely bears some of the responsibility, noting rebel fighters could not have operated the missile "without sophisticated equipment and sophisticated training, and that is coming from Russia."
Russia has denied any involvement, and President Vladimir Putin said Ukraine's military campaign against the rebels was to blame. He also has called for a "thorough and objective investigation" of the crash.
The rebels have denied possessing the launchers.