HRABOVE, Ukraine/WASHINGTON (Reuters) - United States President Barack Obama said the downing of a Malaysian jetliner in a Ukrainian region controlled by Russian-backed separatists should be a "wake-up call for Europe and the world" in a crisis that appears to be at a turning point and warned Russia of possible tightening of sanctions.
While stopping short of blaming Russia for Thursday's crash of Malaysia Airlines flight MH17, in which 298 people died, Mr Obama accused Moscow of failing to stop the violence that made it possible to shoot down the plane.
The United States has said the jetliner was hit by a surface-to-air missile fired from rebel territory.
A senior US official said there was increasing confidence that the missile was fired by separatists and that there was no reason to doubt the validity of a widely circulated audiotape in which voices identified as separatists discussed the downing of the plane.
"This certainly will be a wake-up call for Europe and the world that there are consequences to an escalating conflict in eastern Ukraine; that it is not going to be localized, it is not going to be contained," Mr Obama told reporters on Friday.
Mr Obama spoke by phone later with German Chancellor Angela Merkel, British Prime Minister David Cameron and Australian Prime Minister Tony Abbott. The White House said they discussed Ukraine and the downed jet and the need for an unimpeded international investigation into what happened.
International observers said gunmen stopped them examining the site properly when they got there on Friday. More than half of the victims were Dutch in what has become a pivotal incident in deteriorating relations between Russia and the West.
Mr Obama ruled out military intervention, but said he was prepared to tighten sanctions.
Russia, which Mr Obama said was letting the rebels bring in weapons, has expressed anger at implications it was to blame, saying people should not prejudge the outcome of an inquiry.