Pulitzer Prize - winning journalist Seymour Hersh says the US government has “cherry - picked intelligence” against the Syrian government regarding the Aug. 21 chemical attack in Syria.

Though President Barack Obama eventually decided not to strike Syria, the administration made a public case of the chemical attack for war by saying that Syrian government was responsible for a poison gas attack in the outskirts of Damascus.

The blame was strongly rejected by Syrian President Bashar al - Assad while his government provided United Nations with several reports that showed foreign - backed militants were responsible for it.

The UN later concluded the attack had involved the nerve agent sarin.

In his piece - - titled " Whose Sarin? " - - Hersh reported that, “Obama did not tell the whole story”.

In the his article, Hersh mentioned the Washington Post ' s Aug. 29 report on the US government ' s secret " black budget " for intelligence programs.

He wrote that the leaked document revealed that " the NSA no longer had access to the conversations of the top military leadership in Syria. "

Israeli and US spying agencies had claimed that they have recovered conversations that showed elements in the Syrian government had ordered sarin.

No document was ever released on the claim.

Secondly, the sensors the Americans(or someone) had planted near Syrian chemical arms caches detected nothing in the days prior to the attack, Hersh says. If Assad had launched the sarin - packed missiles, alarm bells would’ve gone off in Washington, but they didin’t.

Hersh’s report said al - Nusra Front terrorist group, al - Qaeda’s and Syrian opposition’s strongest force on the ground fighting against the army, had " mastered the mechanics of creating sarin and was capable of manufacturing it in quantity. ”

" In the months before the attack, the American intelligence agencies produced a series of highly classified reports, culminating in a formal Operations Order – a planning document that precedes a ground invasion – citing evidence that the al - Nusra Front, a jihadi group affiliated with al - Qaeda, had mastered the mechanics of creating sarin and was capable of manufacturing it in quantity. When the attack occurred al - Nusra should have been a suspect, but the administration cherry - picked intelligence to justify a strike against Assad. "

Even as US government officials told Congress and the public that only government forces had access to sarin, the administration knew otherwise: " An intelligence document issued in mid - summer dealt extensively with Ziyaad Tariq Ahmed, a chemical weapons expert formerly of the Iraqi military, who was said to have moved into Syria and to be operating in Eastern Ghouta. The consultant told me that Tariq had been identified ‘as an al - Nusra guy with a track record of making mustard gas in Iraq and someone who is implicated in making and using sarin. ’ He is regarded as a high - profile target by the American military. ”

" On 20 June a four - page top secret cable summarizing what had been learned about al - Nusra’s nerve gas capabilities was forwarded to David R. Shedd, deputy director of the Defense Intelligence Agency. ‘What Shedd was briefed on was extensive and comprehensive, ’ the consultant said. ‘It was not a bunch of " we believes. " ’ He told me that the cable made no assessment as to whether the rebels or the Syrian army had initiated the attacks in March and April, but it did confirm previous reports that al - Nusra had the ability to acquire and use sarin. "

The real smoking gun in Hersh’s piece is the statement attributed to a former senior intelligence official that the " intelligence " cited by administration officials as justification for bombing Syria was simply made up in much the same way that the Bush administration manipulated intelligence - gathering in the run up to the Iraq war. Apparently those sensors had gone off last December, and the NSA had picked up transmissions that seemed to indicate a sarin attack was imminent – but it turned out to be a training exercise. According to Hersh, in making their case for war the administration tried to pass off the December intercepts as having occurred in the days prior to the August 21 incident:

" The former senior intelligence official explained that the hunt for relevant chatter went back to the exercise detected the previous December, in which, as Obama later said to the public, the Syrian army mobilized chemical weapons personnel and distributed gas masks to its troops. The White House’s government assessment and Obama’s speech were not descriptions of the specific events leading up to the 21 August attack, but an account of the sequence the Syrian military would have followed for any chemical attack. ‘They put together a back story, ’ the former official said, ‘and there are lots of different pieces and parts. The template they used was the template that goes back to December. ’ "

The chemical attack case concluded with a UN resolution, backed by the Syrian government, that ordered to have Syria’s chemical weapons destroyed.

The UN resolution, which was adopted on 27 September by the Security Council, dealt indirectly with the notion that militant forces such as al - Nusra front would also be obliged to disarm: ‘no party in Syria should use, develop, produce, acquire, stockpile, retain or transfer[chemical] weapons. ’

The resolution also calls for the immediate notification of the Security Council in the event that any ‘non - state actors’ acquire chemical weapons. While the Syrian government continues the process of eliminating its chemical arsenal, “the irony is that”, al - Nusra and their extremist allies could end up as the only faction inside Syria with access to the ingredients that can create sarin.

Hersh is best known these days for his work in The New Yorker, where he helped break the Abu Ghraib scandal in 2004.