US President Barack Obama has given the clearest indication yet of who might be responsible for the shooting down of Malaysia Airlines Flight 17, saying that the plane was hit by surface-to-air missiles in an area of Ukraine controlled by Russian-backed separatists.
While he stopped short of directly pointing the blame at Russian President Vladimir Putin - saying it was too early to say with certainty who fired the missile - Mr Obama made clear line between the separatists and Russia.
Without Russian support, he said: "It is not possible for these separatists to function how they're functioning."
And regardless of who is responsible for the downing of the plane, Mr Obama said that Mr Putin had the power to put an end to the violence: "He has the most control over that situation and, so far, he has not exercised it."
Ukraine, Russia and the pro-Russian separatists have thus far all denied responsibility for the tragedy.
Speaking at the White House on Friday morning, Mr Obama also revealed that there was an American passenger onboard, someone he identified as Quinn Lucas Schansman. The nationalities of four of the 298 people who were on board remain unverified.
The crash, coming just a day after the United States announced a new round of sanctions against Russia will now likely increase the pressure on US allies in Europe to act. Thus far, nations like Germany and France - which have deep economic ties with Russia - have not taken the same stand as the US on the Ukraine issue. France recently agreed to sell Mistral helicopter carriers to Moscow.
Mr Obama said that the incident "brings home the degree to which the stakes are high in Europe".
"This certainly will be a wake up call for Europe and the world that there are consequences to escalating conflict in eastern Ukraine and it is not going to be localised if it is not going to be contained," he said.
He also said Russia, pro-Russia separatists and Ukraine must adhere to an immediate ceasefire. "It's important for us to recognise that this outrageous event underscores that it is time for peace and security to be restored in Ukraine," he added.
The US president's comments came just hours after a US diplomat delivered a strong criticism of Russia at a meeting of the UN Security Council. US Permanent Representative to the UN Samantha Power called for an urgent independent investigation to be conducted.
"If indeed Russian-backed separatists were behind this attack on a civilian airliner, they and their backers would have good reason to cover up evidence of their crime. Thus, it is extremely important that an investigation be commenced immediately," she said.