The Pentagon has said Russia was supplying air defence system to the Ukrainian separatists believed to have shot down the Malaysian airliner earlier this month killing all of the nearly 300 people on board.
"We do believe that some of the air defence systems that continue to flow up to the border and then across the border are of sufficient range and equivalent capability as to what we saw shoot down the Malaysia airlines flight," Pentagon Press Secretary Rear Admiral John Kirby told reporters.
White House and Pentagon officials had previously charged that a Russian surface-to-air missile system fired by the separatists in eastern Ukraine brought down Malaysian Airlines Flight 17.
"It is not an insignificant capability that we continue to see flow into the hands of the separatists," Kirby said, demanding Russia to stop supporting the separatist movement.
He said Russian military personnel, around 10,000 in number, continue to gather at the border with Ukraine.
"These are combined arms-type battalion tactical groups. They are capable across a wide spectrum of military operations, so it's not just infantry. It's artillery. It's air defence. And in some cases, you know, armoured capability," he said.
"These are very capable, very ready forces," he added.
Kirby claimed that advanced weapons systems, including multiple rocket launchers, artillery weapons, tanks, and air defence systems, continue to move across the border.
"We continue to see that movement across the border, ostensibly to support the separatists," he said