WASHINGTON — The revelation that the United States has "some degree of varying confidence" that the Syrian regime has used chemical weapons brought calls from conservatives in Washington to intervene in the conflict.
The announcement by Secretary of Defence Chuck Hagel in Abu Dhabi marked the first time the US has conceded such suspicions, even in such a qualified form.
It increased expectations that Washington will get involved beyond providing humanitarian help for the rebels in the two-year-old conflict, putting US President Barack Obama on the "horns of a dilemma," as Kenneth Pollack of Brookings Institution, a Washington think tank, wrote.
The US has refused to arm the rebels. But Obama has declared that any evidence that the regime has used chemical weapons would be a "game changer." Senators John McCain and Lindsey Graham on Thursday declared that a "red line" has been crossed.
Nonetheless, the White House quelled any expectation it would rush into military engagement, reminding McCain in a letter of the dangers of uncorroborated intelligence in "our own recent experience" — a clear reference, analysts said, to the trumped up intelligence evidence presented by the administration of president George W Bush to justify invading Iraq in 2003.
"Only credible and corroborated facts that provide us with some degree of certainty will guide our decision-making, and strengthen our leadership of the international community," the White House wrote.
Some analysts said the White House had raised the bar impossibly high in order to avoid involvement.
"Washington has twisted itself into the proverbial pretzel trying to avoid a deeper engagement in the Syrian civil war," Pollack wrote. "Over the past two years, their excuses for inaction have multiplied and morphed in a shameless fashion."
But others pointed out uncertainty about the findings. The White House said the "chain of custody (of evidence) is not clear ... we have an obligation to fully investigate any and all evidence of chemical weapons use within Syria."
Gregory Koblentz, an expert in weapons of mass destruction with the Council on Foreign Relations, told dpa: "'Varying degrees of confidence' does not indicate a lot of faith in the evidence they have in hand."
A White House official said that it was very important to have "airtight" information to underpin decision-making — a level of evidence that would be hard to reach, Koblentz said.
"If the administration wants airtight evidence before acting, they are setting an extremely high threshold that would be extremely hard to meet under the current situation," Koblentz told dpa.
There is danger however if the US is seen as backing away from Obama's earlier declaration about red lines and game changers.
"If (Syrian President Bashar) Assad sees any equivocation on the red line, it will embolden his regime," warned Speaker of the House of Representatives John Boehner, a Republican.
Pollack warned that failure to intervene could make the regime believe "that it can use chemical warfare with impunity," making the war and its spillover into neighbouring states many times worse. An estimated 70,000 people have died in the conflict, and more than 1 million people have been internally displaced or forced to flee to neighbouring Turkey, Lebanon, Jordan and Iraq.
The disastrous consequences of Iraq and the price paid in human life and material hovers like a constant shadow over any decision by the United States to become involved militarily in the volatile Middle East.
Obama never gave details of the consequences he had in mind, and even McCain and Graham called called only for a no-fly zone to ground the Syrian air force, keep government tanks and artillery from moving and protect the rebels.
Koblentz said it would be extremely difficult to determine if chemical weapons were used "weeks and months after it happened" from thousands of miles away and without placing agents or sensors on the ground in Syria, he told dpa.
If Syria would allow the United Nations fact-finding team, now in Cyprus after Damascus requested such an investigation, then refused entry, could go in, it could help piece together the mosaic by gathering soil samples and communication intercepts, Koblentz said.
He supported the White House's requirement for corroboration. "There has to be a threshold of evidence that you need to satisfy before making a major foreign policy decision of this kind," he said.
Even critics of White House reluctance conceded that intervention in Syria would be fraught with danger, require ground battles, hundreds of air sorties and thousands of troops.
"Doing so would require a huge effort, precisely on the scale of Iraq because 'solving' the Syrian civil war would require an effort tantamount to the surge in Iraq, but lasting longer to prevent the slide back into civil war that we are seeing in Iraq today," Pollack wrote.