At a Pentagon briefing held just moments ago about the downing of Malaysian Airlines Flight MH17, Rear Admiral John Kirby said the U.S. believes Russia continues to support pro-Russian separatists with military equipment and financial support, and allows them to enter Ukraine freely.
In regard to the use of the BUK surface to air missile system being used to shoot down Malaysia Airlines flight 17, Kirby said,
"It strains credulity to think that it could be used by separatists without at lease some measure of Russian support and technical assistance. I don't have any indication now that a [SAM] system was brought over and we don't exactly know who is responsible for firing that missile, or with what. That system is fairly sophisticated."
NBC Pentagon Correspondent Jim Miklaszewsky asked Kirby asked if their level of assistance included Russian forces crossing the border into Ukraine, working as advisors or trainers side-by-side with separatists.
Kirby responded that Russia has sent their own aircraft over the border, so "there's no reason to suspect that they haven't provided some measure of support. Nobody is suggesting that Russian military assistance hasn't somehow crossed that border."
Kirby also stated that the motive for the attack remains unclear. "We don't have a working theory at this point. This just happened yesterday." Investigators will have to determine whether the target was assumed to be a military plane, or if it was purely an act of terrorism.