(Adds Russian comment)
By Michelle Nichols
UNITED NATIONS, July 18 (Reuters) - The United States said on Friday it could not rule out Russian help to separatists in Ukraine in firing an SA-11 surface-to-air missile that likely downed a Malaysian airliner in eastern Ukraine with 298 people on board.
U.S. Ambassador to the United Nations Samantha Power told the U.N. Security Council that a Malaysian Airlines Boeing 777 was "likely downed by a surface-to-air missile ... operated from a separatist-held location in eastern Ukraine."
"Because of the technical complexity of the SA-11, it is unlikely that the separatists could effectively operate the system without assistance from knowledgeable personnel. Thus we cannot rule out technical assistance from Russian personnel in operating the systems," Power said.
While Ukraine had SA-11 systems in its inventory, Washington was not aware of any of those systems being in the area where the plane was downed on Thursday, Power said. She added that the Ukrainian military had not fired any missiles during the crisis.
Russia's U.N. Ambassador, Vitaly Churkin, warned against any attempts to pressure an investigation by "trying to prejudge its outcome with broad statements and insinuations that are unjustified in such a difficult situation."
He said there should be an "impartial, open investigation of what happened" and that Moscow believed an international commission should be created under the U.N. International Civil Aviation Organization.
Churkin questioned why Ukrainian aviation dispatchers sent the flight into "an area of military clashes, an area which was used to carry out strikes against civilian targets and where there were anti-aircraft systems working."
"Ensuring the security and effective use of civilian aviation in an airspace of a state is the responsibility of that state in line with international standards," he said.
The U.N. Security Council on Friday called for a "full, thorough and independent international investigation" into the downing of the Malaysian airliner, urging all parties to grant investigators access to the site.
In a statement agreed by consensus, the council also called for "appropriate accountability." Britain drafted the short text and hoped the 15-member council could issue it on Thursday, but Russia requested more time to review it before it was agreed.
U.N. political affairs chief Jeffrey Feltman told the Security Council that he would travel to Moscow and Kiev in the coming days. He also said ICAO made an offer to Ukraine to put together an international team of investigators. (Additional reporting by Mirjam Donath; Editing by Chizu Nomiyama and James Dalgleish)