Malaysia Airlines MH17 crash and US intelligence
A Malaysian air crash investigator inspects the crash site of Malaysia Airlines Flight MH17, near the village of Hrabove (Grabovo), Donetsk region.Reuters

The US intelligence officials are unsure who was exactly behind the attack which brought down the Malaysia Airlines flight MH17 over Ukrainian airspace.

While the officials insisted that the "most plausible" explanation could be Ukrainian separatists downing the aircraft "by mistake," they failed to point fingers at the exact perpetrators.

They spoke to a selected group of reporters under the agreement that their names remain anonymous.

"We don't know who literally was operating the system that day but more generally we have the picture of evidence that says the Russians have been providing these types of systems, the Russians have been providing training," said an official, without divulging the specifics of the event, according to multiple media reports.

When pressed further, however, the officials admitted: "We don't know a name, we don't know a rank, and we're not even 100 percent sure of a nationality."

They suspect an "ill-trained crew" relied solely on the radar system which is part of the SA-11 surface-to-air missile battery system, which may not have differentiated between a fighter aircraft and a civilian plane.

Entirely depending on the radar, which is designed to be used in an "integrated air defence system", could have provided the crew with a "much more fuzzy picture" of the air traffic, the American officials say.

The intelligence, in addition to phone intercepts and other satellite images, have also cited social media postings – which are so far unverified and their original sources not established – for their claims.

Nonetheless, the officials have emphasised that Moscow has helped create the necessary atmosphere for the attack to take place.

"It's a solid case that it's a SA-11 that was fired from eastern Ukraine under conditions the Russians helped create," a senior official at the briefing said.

US President Barack Obama, on 21 July, said the Boeing 777 passenger plane with 298 people on board "was shot down over territory controlled by Russia-backed separatists".

White House Deputy National Security Adviser Ben Rhodes told CNN that Washington is still examining whether Moscow has any "direct link" in downing the plane.

Rhodes said in the interview: "We do think President Putin and the Russian government bears responsibility for the support they provided to these separatists, the arms they provided to these separatists, the training they provided as well and the general unstable environment in eastern Ukraine."