WASHINGTON -- Senior U.S. intelligence officials said Tuesday that Russia was responsible for "creating the conditions" that led to the shooting down of Malaysia Airlines Flight 17, but they offered no evidence of direct Russian government involvement.
The intelligence officials were cautious in their assessment, noting that while the Russians have been arming separatists in eastern Ukraine, the U.S. had no direct evidence that the missile used to shoot down the passenger jet came from Russia.
The officials briefed reporters Tuesday under ground rules that their names not be used in discussing intelligence related to last week's air disaster, which killed 298 people.
The plane was likely shot down by an SA-11 surface-to-air missile fired by Russian-backed separatists in eastern Ukraine, the intelligence officials said, citing intercepts, satellite photos and social media postings by separatists, some of which have been authenticated by U.S. experts.
But the officials said they did not know who fired the missile or whether any Russian operatives were present at the missile launch. They were not certain that the missile crew was trained in Russia, although they described a stepped-up campaign in recent weeks by Russia to arm and train the rebels, which they say has continued even after the downing of the commercial jetliner.
In terms of who fired the missile, "we don't know a name, we don't know a rank and we're not even 100 percent sure of a nationality," one official said, adding at another point, "There is not going to be a Perry Mason moment here."
White House deputy national security adviser Ben Rhodes said the U.S. was still working to determine whether the missile launch had a "direct link" to Russia, including whether there were Russians on the ground during the attack and the degree to which Russians may have trained the separatists to launch such a strike.
"We do think President Putin and the Russian government bears responsibility for the support they provided to these separatists, the arms they provided to these separatists, the training they provided as well and the general unstable environment in eastern Ukraine," Rhodes said in an interview with CNN.
He added that heavy weaponry continues to flow into Ukraine from Russia following the downing of the plane.
The intelligence officials said the most likely explanation for the downing was that the rebels made a mistake. Separatists previously had shot down 12 Ukrainian military airplanes, the officials said.
The officials made clear they were relying in part on social media postings and videos made public in recent days by the Ukrainian government, even though they have not been able to authenticate all of it. For example, they cited a video of a missile launcher said to have been crossing the Russian border after the launch, appearing to be missing a missile.
But later, under questioning, the officials acknowledged they had not yet verified that the video was exactly what it purported to be.
Despite the fuzziness of some details, however, the intelligence officials said the case that the separatists were responsible for shooting down the plane was solid. Other scenarios -- such as that the Ukrainian military shot down the plane -- are implausible, they said. No Ukrainian surface-to-air missile system was in range.
From satellites, sensors and other intelligence gathering, officials said, they know where the missile originated -- in separatist-held territory -- and what its flight path was. But if they possess satellite or other imagery of the missile being fired, they did not release it Tuesday. A graphic they made public depicts their estimation of the missile's flight path with a green line. The jet's flight path was available from air traffic control data.
In the weeks before the plane was shot down, Russia had stepped up its arming and training of the separatists after the Ukrainian government won a string of battlefield victories. The working theory is that the SA-11 missile came from Russia, although the U.S. doesn't have proof of that, the officials said.
U.S. Ambassador to the U.N. Samantha Power said last week that "because of the technical complexity of the SA-11, it is unlikely that the separatists could effectively operate the system without assistance from knowledgeable personnel. Thus, we cannot rule out technical assistance from Russian personnel in operating the systems," she said.
Asked about evidence, one of the senior U.S. intelligence officials said it was conceivable that Russian paramilitary troops are operating in eastern Ukraine, but that there was no direct link from them to the missile launch.
Asked why civilian airline companies were not warned about a possible threat, the officials said they did not know the rebels possessed SA-11 missiles until after the Malaysian airliner was shot down.