WASHINGTON, July 20 -- There must be a "prompt, full, unimpeded and transparent" international investigation into the crash of doomed Malaysia airliner, U.S. President Barack Obama and Australian Prime Minster Tony Abbott said in their telephone conversation on Sunday evening.

"The two leaders also agree that Russia has a responsibility to use its extraordinary influence with the pro-Russia separatists who control the crash site to compel them to cooperate with international monitors and investigators," said a statement issued by the White House summarizing the talk between the leaders.

The U.S. State Department said Saturday that it was "deeply concerned" by rebels' refusal to allow monitors safe and unfettered access to the crash site of doomed Malaysia airliner.

"The site is not secure, and there are multiple reports of bodies being removed, parts of the plane and other debris being hauled away, and potential evidence tampered with," said State Department spokeswoman Jen Psaki.

The Malaysia Airliners MH17 flight with 298 people aboard crashed Thursday in eastern Ukraine, with no survivors found so far.

Obama underscored that the U.S. will continue to support and coordinate closely with Australia as this issue move forward, the statement said.