The White House has flatly denied a new report by Pulitzer Prize-winning journalist Seymour Hersh that claims the Obama administration manipulated intelligence reports to support its case for military intervention in Syria.

Hersh, who exposed the My Lai massacre during the Vietnam War and reported American mistreatment of detainees at Iraq’s Abu Graib prison, said the Obama administration “cherry-picked intelligence” to blame Syrian President Bashar al-Assad for an Aug. 21 nerve-gas attack.

“In some instances, (President Barack Obama) omitted important intelligence, and in others he presented assumptions as facts,” Seymour reported Sunday in The London Review of Books.

“Most significant, he failed to acknowledge something known to the US intelligence community: that the Syrian army is not the only party in the country’s civil war with access to sarin, the nerve agent that a UN study concluded -- without assessing responsibility -- had been used in the rocket attack.”

Secretary of State John Kerry said the U.S. had proof that the attack was made on Assad’s orders, and Obama said in a Sept. 10 speech that the revelation had pushed him over the “red line” in considering a military strike on Syria.

A former senior intelligence official told Hersh that the Obama administration had altered the timing and sequence of some available information to give the appearance that it had been picked up and analyzed in real time, as the attack happened.

The official compared the distortion to the 1964 Gulf of Tonkin incident, when the Lyndon B. Johnson administration had reversed the sequence of intelligence intercepts to justify one of the early bombings in North Vietnam.

“(Military and intelligence personnel) are throwing their hands in the air and saying, ‘How can we help this guy (Obama) when he and his cronies in the White House make up the intelligence as they go along?”’ the former official said.

However, a spokesman for the director of national intelligence dismissed Hersh’s report as “simply false.”

"The intelligence clearly indicated that the Assad regime and only the Assad regime could have been responsible for the 21 August chemical weapons attack,” intelligence spokesman Shawn Turner said in a statement to The Hill. “The suggestion that there was an effort to suppress intelligence about a nonexistent alternative explanation is simply false.”

Hersh reported that the White House did not have advanced warning from the assumed source of the attack because, as shown in documents leaked by former intelligence contractor Edward Snowden, the Assad administration had recognized its vulnerability to U.S. eavesdropping and rectified it.

Documents leaked by Snowden formed the basis of a Washington Post report that revealed a secret sensor system that monitored the status of Syria’s chemical weapons arsenal, but Hersh reported that the sensors detected no movement in the months or days before the Aug. 21 attack.

The former intelligence official told Hersh that the sensors had detected movement in December 2012 that caused Obama to issue a public warning to Syria that using sarin was “totally unacceptable.

“If what the sensors saw last December was so important that the president had to call and say, “Knock it off,” why didn’t the president issue the same warning three days before the gas attack in August?” the former intelligence official said.

Hersh reported that the Obama administration buried reports that the jihadi group al-Nusra had “mastered the mechanics of creating sarin” and was capable of making bulk quantities of the deadly chemical agent, which he said undermined the case that Assad had undoubtedly been responsible for the attack.

The freelance reporter is best known recently for his work in The New Yorker, but he told The Huffington Post the publication had “little interest” in his Syria report.

A representative from The New Yorker did not respond to requests for comment.

Buzzfeed reported that The Washington Post had intended to publish the report after Hersh brought it there, but the newspaper ultimately passed on the article.

Hersh said Executive Editor Marty Baron told him by email “that the sourcing in the article did not meet the Post's standards.”

Ultimately, the Obama administration had decided not to strike in retaliation after Russia helped forge an agreement by the Assad regime to turn over its chemical weapons to the international community after the president’s plan for military intervention found little support among U.S. allies or Congress.

[Image: Seymour Hersh by Marjorie Lipan via Flickr]