Samantha Power, US Ambassador to the UN, said that because of the technical complexity of the surface-to-air missile SA-11 operated from a separatist-held location in eastern Ukraine, it is "unlikely" that the separatists could "effectively operate the system without assistance from knowledgeable personnel".
"We cannot rule out technical assistance from Russian personnel in operating the systems. 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. It is extremely important that an investigation be commenced immediately," Samantha said in her remarks to the UN Security Council meeting on Ukraine.
Power shared the US assessment of the evidence into the crash and stated that "of all the operational SAM systems located near the border Russia-Ukraine, only the SA-11, SA-20, and SA-22 SAM systems are capable of hitting an aircraft at the flight’s altitude of 33,000 feet."
The US Ambassador told the UN Council that while Ukrainians have SA-11 systems in their inventory, the US is not aware of any Ukrainian surface-to-air missiles systems in the area of the shoot-down.
"More importantly, since the beginning of this crisis, Ukrainian air defences have not fired a single missile, despite several alleged violations of their airspace by Russian aircraft," Power said.
The official called for a full, credible and unimpeded international investigation that must begin immediately so that the perpetrators are brought to justice.
"They must not be sheltered by any member state of the United Nations," she said.
Power accused Russian President Vladimir Putin of breaking commitments to working towards dialogue and peace.
"Russia has in the last few weeks increased the number of tanks, armored vehicles, and rocket launchers and more advanced air defence systems in southwest Russia," she said.
Power also criticised Moscow over the transfer of Soviet-era tanks and artillery to the separatists and the discovery of huge cache of weapons associated with Russia stockpiles by Ukrainian officials.
"Recruiting efforts for separatist fighters are expanding inside Russia and separatists have openly said that they are looking for volunteers with experience operating heavy weapons such as tanks and air defenses," she said, adding that Russia continues to redeploy new forces extremely close to the Ukrainian border.
The US official said that the attack on the Malaysian airliner follows a "pattern of actions" by Russian-backed separatists who have in the past shot down Ukrainian military planes.
"The context for yesterday’s horror is clear, separatist forces backed by the Russian government continue to destabilise Ukraine and undermine the efforts of Ukraine’s elected leaders to build a democratic Ukraine that is stable, unified, secure and able to determine its own future," Power said.
Power stressed that the Organization for Security and Cooperation in Europe Special Monitoring Mission should act as a first responder and lay the foundation for efforts by other international organisations and individual nations to investigate the incident.
"International investigators must be granted immediate, full and unfettered access to the crash site. All those concerned, Russia, pro-Russian separatists and Ukraine should agree to support an immediate ceasefire to facilitate access by international investigators," she said.
Power added that the evidence at the crash site should remain "undisturbed" and Russia should ensure that any evidence removed from the site by the Russian-backed separatists operating in the area should be promptly returned.
"The tragedy underscores the urgency and determination with which we insist that Russia immediately take concrete steps to de-escalate the situation in Ukraine, support a sustainable cease-fire and follow the path toward peace that the Ukrainian government has consistently offered," Power said.
"This war can be ended. Russia can end this war. Russia must end this war," she added.
The attack on the civilian airliner was also strongly condemned by UN Secretary General Ban Ki-moon who said the "horrifying incident" must "at the very least" prompt a serious and sustained effort to end the fighting in Ukraine.
Ban said there must be accountability for the tragedy and "anyone found to be responsible must be brought to justice."
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Photographs: Maxim Zmeyev/Reuters