Reports that intelligence tying Syrian President Bashar Assad or his top lieutenants to an alleged chemical weapons attack last week is no “slam dunk” are delaying any U.S. response and are likely to stir even more dissent among members of Congress about launching air strikes into Syria.

Members of the U.S. intelligence community say there are serious holes in information they have gathered since the alleged chemical assault outside Damascus about who actually controls Syria’s chemical weapons stockpiles and there are doubts about whether Assad himself ordered the strike, according to an Associated Press report.

With the Obama administration set to brief members of Congress and key national security committees Thursday, the still-unresolved questions about the reported Aug. 20 chemical attack that killed 1,000 people will likely fuel a robust debate about whether the U.S. has enough proof of its claims that Assad’s forces used chemical weapons against its own people.

Many members of Congress, and the Obama administration itself, have deep concerns about the weapons of mass destruction predicate the Bush national security team used to justify starting a war in Iraq that ended up costing the U.S. hundreds of billions of dollars and 4,400 lives and ended in a quagmire after a decade.

Still, President Obama Wednesday unequivocally declared that the Syrian government was responsible for the chemical attacks in an attempt to lay the groundwork for an U.S.-led military strike on Syria.

“We have concluded that the Syrian government in fact carried these out,” Obama said in an interview with “NewsHour” on PBS. “And if that’s so, then there needs to be international consequences.”

Behind the scenes, administration officials are deeply divided on whether to release a report by the Office of the Director for National Intelligence that was supposed to lay the groundwork for military action. The AP quoted multiple U.S. officials using the phrase “not a slam dunk” to describe the intelligence picture.

The phrase is a reference to then-CIA Director George Tenet’s insistence in 2002 that U.S. intelligence undeniably showed that Iraq had weapons of mass destruction – a statement that turned out to be wrong, with grave repercussions that would last a decade.

The report, according to the AP, also concedes that it cannot pinpoint the exact locations of Assad’s supplies of chemical weapons and says the Syrian leader could have moved them in recent days as the U.S. and its allies denounced the apparent attack. Without knowledge of the exact location of the chemical weapons, any military strikes could mistakenly hit stores of sarin gas, widely dispersing the toxins in civilian areas.

Meanwhile, as the U.S. and Britain wrestle with the decision of ordering military strikes, reports are surfacing that Syrian authorities have moved prisoners from their jail cells to installations the government believes could be targets of Western military strikes.

Citing pro-democracy activists, The National, a Middle Eastern newspaper published in English, said residents in the Syrian capital said they had seen fully loaded buses moving late Wednesday from the military court in Damascus to Mezzeh airbase on the southwestern tip of the city, a likely target for U.S. missiles.