US Defense Secretary Chuck Hagel urged caution Wednesday over an Israeli claim that the Syrian regime used chemical weapons, saying all evidence must be weighed carefully as such allegations are "serious business".
Hagel indicated he had been caught off guard by claims from an Israeli general this week that Syria had fired chemical agents against rebels in recent months, the AFP news agency reported.
"When I was in Israel they did not give me that assessment. I guess it wasn't complete," Hagel told reporters in Cairo on a tour of the Middle East that included a three-day visit to Israel.
The United States has warned any use or transfer of chemical weapons would cross a "red line" and possibly trigger military action.
Britain and France also suspect Syria has used chemical weapons but Hagel said American intelligence agencies were still evaluating information and were not yet convinced.
"Suspicions are one thing, evidence is another," he said.
The Pentagon chief added that "this is serious business and you want to be as sure as you can be on these kind of things".
Asked if American credibility could be at risk as it has repeatedly referred to a "red line," Hagel responded by saying, "I don't think there's any danger".
The United States cooperates with other spy services but ultimately had to rely "on its own intelligence," he said before departing for Abu Dhabi.
Hagel's comments marked his first public reaction since the Israeli military's assessment came to light.
While Hagel was concluding his visit to Israel on Tuesday morning, Israeli Brigadier General Itai Brun, head of the research and analysis division of military intelligence, made headlines when he alleged Syrian President Bashar al-Assad's regime had used chemical agents -- mostly likely sarin gas -- more than once.
"To the best of our professional understanding, the (Assad) regime has made use of deadly chemical weapons against the rebels in a number of incidents in the last few months," Brun told a security conference in Tel Aviv.