President Barack Obama is demanding Russian-backed separatists in Ukraine grant international investigators access to the crash site of Malaysian Airlines Flight MH17.
"We have to make sure the truth is out and accountability exists," Obama said Monday from the South Lawn of the White House.
Four days after the Boeing 777 went down over eastern Ukraine, the crash site and all the evidence still remain unexamined. Around 250 bodies have been recovered, most of which were moved to refrigerated rail cars after lying out in the sun for days.
The pro-Russian insurgents have been blocking recovery efforts and confiscating crucial evidence, including the plane's black boxes.
Obama accused them of removing evidence from the crash site.
"What exactly are they trying to hide?" the president asked.
The news comes as new evidence implicates the separatists in the tragedy.
The U.S. says it tracked a missile from rebel territory hitting the Malaysian jet. In addition, there are audio intercepts released by Ukraine rebel leaders discussing the shoot-down.
"We have just shot down a plane," a rebel leader is heard saying in one audio recording.
The U.S. also spotted a Russian convoy carrying military equipment entering Ukraine last week and three anti-aircraft missiles brought in before the shoot-down. The convoy then quickly rushed back across the border into Russia after the incident.
Meanwhile, world outrage is growing.
"I want to arrange a funeral. I can't. I don't know where they are. I want my children back," said Silene Fredriksz-Hoogzand, whose son, Bryce, and his girlfriend, Daisy Oehlers, were among those killed.
Russian President Vladimir Putin is lashing out against criticism for Moscow's role in fomenting the unrest that led to the tragedy.
Putin's accusing others of exploiting the crash for so-called "mercenary objectives." The Russian leader is also still blaming Ukrainian authorities for reigniting the fighting with the pro-Russian rebels.
But Secretary of State John Kerry was having none of that.
"Russia has armed the separatists. Russia has supported the separatists. Russia has trained the separatists. Russia continues to refuse to call publicly for the separatists to engage in behavior that would lend itself to a resolution of this issue," Kerry charged.
Ukrainian Prime Minister Arseniy Yatsenyuk is calling the MH17 crash a "crime against humanity."
"All red lines have been already crossed. This is the deadline," Yatsenyuk said in a statement Friday.
"We ask our international partners to call an emergency UN Security Council meeting and to make everything we can to stop this war -- a war against Ukraine, a war against Europe. And after these terrorists shot down a Malaysian aircraft -- this is a war against the world," he said.
Meanwhile, Obama is being criticized for not being forceful enough.
"President Obama is trying to be deliberative," Sen. Lindsey Graham, R-S.C., said. "It comes off as indecisive. He's trying to be thoughtful. It comes off as weakness."
"The Europeans are never going to lead on this issue," he warned. "It's indispensable that America lead."