The United States said Thursday for the first time that Syria had likely used chemical weapons against rebel forces, but emphasized spy agencies were still not 100 percent sure of the assessment, AFP reports.
A senior White House official said that "all options are on the table" should use of the chemical weapons be confirmed, but a U.S. defense official stressed that a military intervention was not imminent and signaled spy agencies had differing opinions.
"Our intelligence community does assess with varying degrees of confidence that the Syrian regime has used chemical weapons on a small scale in Syria," U.S. National Security Council spokeswoman Caitlin Hayden said, according to AFP.
The assessment, which she said was based in part on "physiological samples," points to the possible use of sarin, a man-made nerve agent used in two attacks in Japan in the 1990s. It can cause convulsions, respiratory failure and death.
Hayden, however, warned the chain of custody of the weapons was "not clear, so we cannot confirm how the exposure occurred and under what conditions."
"Given the stakes involved, and what we have learned from our own recent experience, intelligence assessments alone are not sufficient," she said, according to AFP.
U.S. Defense Secretary Chuck Hagel, speaking in Abu Dhabi, said the decision to release the intelligence report had been "made within the past 24 hours" and warned that use of such weapons "violates every convention of warfare."
A U.S. defense official traveling with Hagel confirmed that the phrase "varying degrees of confidence" is a term commonly used by the intelligence community to indicate disagreement among various agencies.
But the assessment reflected a degree of certainty that Syria most likely has fired chemical agents and was not merely a tentative suspicion, the official said.
In London, Britain's Foreign Office too said it had "limited but persuasive" evidence of the use of chemical agents in Syria's grinding civil war, which the UN says has left more than 70,000 people dead since it began in March 2011.
Mounting evidence of chemical weapons attacks on fighters battling Assad's regime could increase the pressure on U.S. President Barack Obama -- who has sought to avoid any U.S. military role in the conflict -- to intervene.
"All options are on the table, in terms of our response, and it could run a broad spectrum of activity across our various types of efforts in Syria," a senior White House official said, adding that Washington was consulting with its allies.
Earlier this week, an Israeli general in military intelligence alleged that Syria had used chemical agents more than once during the protracted civil war, after Britain and France had voiced similar concerns to the United Nations.
Asked if the intelligence assessment meant that Syria had passed the declared "red line," Hagel said that was a policy question and that his task was to provide the U.S. president with "options."
Chemical weapons are "uncontrollable deadly weapons" that most leaders view as being in a "different category," Hagel said at the end of a Middle East tour of Israel, Jordan, Saudi Arabia, Egypt and the United Arab Emirates.
Syria’s Information Minister claimed on Wednesday that Damascus will not use chemical weapons against its own citizens, or in the event of war with its neighbor Israel.
Minister Omran al-Zoubi said Syria would not resort to chemical weapons even if it had to go to war with Israel and use "all resources.”
"Even if Syria does have chemical weapons, our leadership and our military will not use them either against Syrians or against Israelis, above all for moral reasons and secondarily on legal and political grounds," Zoubi reportedly said at a Moscow university.