It has been four days since Russian-backed separatists in Ukraine shot down -- reportedly with a surface-to-air missile -- the Malaysian airliner, killing nearly 300 people aboard, including one American.
While the immediate focus is on recovering the bodies of those killed in the incident, the president said, investigating exactly what happened and putting forward the facts is also a priority.
Obama noted that international investigators are on the ground and are ready to conduct their work.
"What they need right now is immediate and full access to the crash site," the president said. "They need to be able to conduct a prompt and full and unimpeded, as well as transparent, investigation."
Ukraine President Petro Poroshenko has declared the areas around the crash site a demilitarized zone, but the Russian-controlled separatists who control the area continue to block the investigation.
The separatists have barred investigators from the scene, and they are removing evidence from the crash site, "all of which begs the question, what are they trying to hide?" the president asked.
Russia has extraordinary influence over these separatists, Obama said. The separatists are Russian-sponsored, Russian-trained and Russian-equipped. This last includes supplying anti-aircraft weapons to the separatists. All of the separatists' key leaders are Russian citizens.
Given this, Russian President Vladimir Putin has the direct responsibility to compel the separatists to cooperate with the investigation, Obama said.
"Russia must tell separatists to stop tampering with evidence and grant access to crash sites," the president said.
As investigative work gets underway, the Russians and the separatists are responsible for the safety of the investigation teams, Obama said.
The president emphasized that a diplomatic solution is still his preference for the situation in Ukraine, where pro-Russian separatists have been battling Ukraine government forces.
By its actions in Ukraine, Russia "will only further isolate itself from the international community and the costs for Russia's behavior will only increase," Obama said.
Obama called on Putin to "pivot away from the strategy they've been taking and get serious about resolving hostilities in Ukraine in a way that respects Ukraine's sovereignty and respects the right of the Ukrainian people to make their decisions about their own lives."