The Pentagon said Tuesday that Russia was supplying separatists in Ukraine air defense systems similar to the one that brought down Malaysia Airlines Flight 17.
"We do believe that some of the air defense 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," said Pentagon press secretary Navy Rear Adm. John Kirby.
"So it's not an insignificant capability that we continue to see flow into the hands of the separatists," Kirby said Tuesday at a Pentagon briefing.
The administration has tried to ramp up the pressure on Russia in the past week, in advance of new U.S. and European Union sanctions on Russia.
Pentagon officials said last week that Russia was continuing to supply weapons to pro-Russia separatists in Ukraine, and was poised to supply heavier rocket systems. They said Russian forces are also firing across the border onto Ukrainian military positions.
Kirby said Russia was supplying the separatists with multiple rocket launch systems, artillery systems, tanks and air defense systems.
In addition, they said there were upwards of 10,000 Russian troops positioned closer to the border than they were in March, after Russia annexed Crimea.
"These are combined arms-type battalion tactical groups. What I mean by that is that they are capable across a wide spectrum of military operations, so it's not just infantry. It's artillery. It's air defense. And in some cases, you know, armored capability," Kirby said.
"These are very capable, very ready forces," he said.
The Ukrainian defense minister on Monday requested more military assistance from the Pentagon on Tuesday, but officials have not discussed what those requests are.
The Pentagon has provided a number of non-lethal aid items to Ukraine, including package meals, sleeping mats, radios and helmets, and says it is still reviewing further requests.
"We continue to look at requests coming from the Ukrainian government. There is an interagency review process for that," Kirby said. "We have been focused on the non-lethal side, but as we have been before, we're open to considering more immediate requests by the Ukrainian government."