Washington (CNN) - Most Americans say Russia is directly or indirectly responsible for the downing of a Malaysia Airlines jetliner over eastern Ukraine, and unfavorable opinions of Russia have surged, according to a new national poll.
A CNN/ORC International survey conducted Friday through Sunday also indicates that nearly nine in 10 say that Moscow and pro-Russian rebels that control the area where Flight 17 crashed last week will try to cover something up in any international investigation.
But only one in 10 say the United States should take military action if there is clear evidence that Russia is responsible for the shooting down of the plane, which killed all 298 passengers and crew.
U.S. and other officials have said it appears the plane was shot down by a sophisticated surface-to-air missile. While they have stopped short of putting the responsibility squarely on Russia, President Barack Obama and others have said the rebels could not have acted without weapons and training from Russia.
Release of the poll comes as Obama lashed out at Moscow over conditions at the crash site, saying the rebels continue to impede efforts to recover bodies and investigate exactly what happened.
He called on Russia to rein in the rebel fighters, who he said had treated remains poorly and removed evidence.
"What exactly are they trying to hide?" Obama asked.
According to the poll, just 19% of Americans have a favorable opinion of Russia, down from 41% in February. Fifty-seven percent of the public saw Russia in a positive way in a 2011 CNN/ORC survey.
Seventy-eight percent of those questioned say they have an unfavorable opinion of Russia, a surge of 23 percentage points since February. Only 40% of Americans in the 2011 CNN poll had a negative view of Russia.
"Negative views of Russia are up across the board, but some of the biggest changes come among women and younger Americans," said CNN Polling Director Keating Holland.
"A bare majority of Americans under the age of 50 had a favorable view of Russia in February, but now that number has dropped 27 points. That may be due to the fact that older Americans are more likely to remember the Cold War and take a less optimistic view of Russia. Positive views of Russia are also down 26 points among women, compared to 18 points among men," Holland added.
Who's to blame?
Fifty-six percent of the public said it is very likely that rebel groups launched the missile that brought down Flight 17, according to the survey. Another 24% believe that it's somewhat likely and only one in seven think it's unlikely.
Just over a third said Moscow is directly responsible for the disaster, with another 51% saying Russia's indirectly responsible.
"That leaves only 11% who say that Russia had nothing to do with the attack," Holland added.
And only 7% say they trust Russia and the separatist groups in eastern Ukraine to fully cooperate with the international investigation. More than nine in 10 say they think Moscow and the separatists will try to cover something up.
Hours before the poll's release, Obama said it was time for Russia to exert what he called its "enormous influence" over the rebel fighters to persuade them to better cooperate with the international investigation.
"It's the least they can do," Obama added.
A representative for the rebels in Ukraine told CNN that the Boeing 777's "black box" cockpit voice and flight data recorders would be handed over to Malaysian investigators on Monday night.
How should the U.S. respond?
If there is clear evidence that Russia is responsible for the crash, more than seven in 10 said the United States should exert economic or diplomatic sanctions against Moscow, with 19% saying Washington should take no action at all. Only 9% said America should take military action.
The poll was conducted for CNN by ORC International from July 18-20, with 1,012 adult Americans questioned by telephone. The survey's overall sampling error is plus or minus three percentage points.