A Syrian rebel military leader said Wednesday that he is convinced Israeli Mossad agents are operating in Syria, claiming their presence in the war-torn country was what led the IDF to state that chemical weapons were used by the Assad regime.

“Israel has this information because there are many, many members of security services who are now very active in Syria,” Free Syrian Army Chief of Staff General Salim Idriss told CNN’s Christian Amanpour, hinting that the weakened regime of President Bashar Assad was incapable of controlling the borders. “Mossad is one of the most famous security services in the world and I don’t think they are away.”

Speaking at a security conference in Tel Aviv on Tuesday, IDF intelligence analyst Brig. Gen. Itai Brun said that based on the pictures of victims in Syria — the size of their pupils, “and the foam coming out of their mouths” — the army believed that Assad’s troops had used the lethal nerve gas sarin as a weapon and that it had been used on more than one occasion, including in a specific attack on March 19.

The US, which has said chemical weapon use would be a “red line” necessitating intervention, was quick to distance itself from the report, saying it could not confirm the use of sarin. The US, both before and after Brun’s statement, has gone out of its way to avoid making that kind of declaration.

“We are looking for conclusive evidence, if it exists, if there was use of chemical weapons,” Jay Carney, the White House press secretary, said later Tuesday.

In Brussels, Secretary of State John Kerry rushed to declare that Prime Minister Benjamin Netanyahu was “not in a position to confirm” Brun’s assessment and, on Wednesday, Defense Secretary Chuck Hagel said he was caught by surprise by the IDF analyst’s definitive statement, adding that the information was not shared with him during his visit to the country earlier this week.

Both the UK and France have claimed to be in possession of credible evidence that Syria has used chemical weapons on more than one occasion since December, citing soil samples taken from Syrian battlegrounds.

On Wednesday, Syria denied it had or would contemplate using chemical weapons, saying it would not deploy nerve agents “even against Israel.”

“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,” Information Minister Omran al-Zoubi said during a visit to Moscow University, according to a report by Russia’s Interfax news agency quoted by Reuters.

Israel’s ambassador to the United Nations on Wednesday warned the UN Security Council that Hezbollah, allied with Assad, was close to getting its hands on Syria’s massive stockpile of chemical weapons.

“In Lebanon, Hezbollah is building an army equipped with 50,000 missiles — more than many NATO members. Now they might have access to one of the largest stockpiles of chemical weapons in the world,” Ron Prosor said.

Mitch Ginsburg and Josh Davidovich contributed to this report