The Obama administration has been documenting the escalating use of chemical weapons by the Bashar Assad regime in Syria for more than a year, recording a much higher number of incidents than previously thought, US officials said.

According to a report in the Los Angeles Times late Friday, top US lawmakers were first briefed on the use of such weapons in July 2012 — a month before US President Barack Obama would announce his “red lines.” US officials who saw the intelligence, however, said the intelligence for that incident was inconclusive.

But it was the beginning of a stream of information on the escalating use of chemical weapons by the regime.

On Wednesday, US Secretary of State John Kerry said the administration knew of at least 11 incidents where Assad used chemical weapons even before the August attack, which is more than double the number the US had previously divulged.

But the administration did not go public with the information, saying that it believed Assad used chemical weapons only in April this year, a month after a March sarin attack in Syria went awry and also killed government troops.

“The president didn’t believe it was a compelling enough case to win the support of the American people and the world,” Kerry told lawmakers when he was asked why the US didn’t push for military action in April.

Chemical attacks, said US officials cited in the report, started small — for the “psychological impact” — and grew larger as they were met with no international response. in some cases, Assad forces used a single shell in a given area, killing 10 people at a time, or less.

In June this year, as the evidence was becoming hard to ignore, according to the report, White House deputy national security adviser Ben Rhodes announced that “our intelligence community assesses that the Assad regime has used chemical weapons, including the nerve agent sarin, on a small scale against the opposition multiple times in the last year.”

He cited four attacks: March 19 and April 13 near Aleppo; May 14 in the town of Qasr Abu Samra; and a May 23 attack in the eastern part of Damascus.

The intelligence, he said, included “reporting regarding Syrian officials planning and executing regime chemical weapons attacks; reporting that includes descriptions of the time, location and means of attack; and descriptions of physiological symptoms that are consistent with exposure to a chemical weapons agent.”

In response, the US then announced a plan to train rebels and increase aid in the form of weapons distribution — but the whole program has been slow moving and has had little impact on the ground.

Some say the evidence available for previous attacks was not “compelling” and could not be used convincingly to make the case for a response, while others suggest that had the US intervenes earlier, Assad could have been deterred from carrying out the August 21 attack in a Damascus suburb — which the US says killed 1,429 people.

Rep. Mike Rogers (R-Mich.), who chairs the House intelligence committee, was quoted by the LA Times as saying that had the Obama administration responded more forcefully to earlier attacks, the further use of chemical weapons could have been deterred.

“All the forensic evidence, everything you see with this attack, we had with previous attacks,” said Rogers.

“The only difference is, this one was on the front page of the newspaper. That is a horrific standard…. We dithered, and the result is you get the front-page attack and we get to see hundreds of dead children,” he added.

Obama has been working for several weeks to gain international and domestic support for a US-led strike in Syria in response to the August 21 attack. He’s already secured the support of a Senate panel that authorized the order to strike, provided that any operation last no more than 90 days and that no American troops set foot in Syria. He’s now lobbying for congressional approval, as Congress reconvenes next week.