Defense Secretary Chuck Hagel said Wednesday that Israeli military leaders kept him in the dark, during three days of face-to-face meetings, about their assessment that forces loyal to the Syrian government have killed rebel fighters with chemical weapons.

An Israeli general made the assertion Tuesday at a conference in Tel Aviv while Hagel was in the country meeting with Prime Minister Benjamin Netanyahu and Defense Minister Moshe Yaalon. Hagel said Wednesday that the Israelis did not mention their finding even though the two sides had discussed at length common concerns about the threat posed by Syria’s chemical weapons stockpile.

“They did not give me that assessment. I guess it wasn’t complete,” Hagel told reporters in Cairo during a stop on a week-long visit to the Middle East. “I haven’t seen the specifics.”

The Israeli general’s claim, repeated shortly afterward by another senior Israeli military official, came less than a week after France and Britain made similar assertions to the United Nations.

The findings by three close U.S. allies intensify pressure on Washington to intervene militarily in the Syrian civil war. Despite its reluctance to become directly involved in the conflict, the Obama administration has repeatedly declared that it would not tolerate the use of chemical weapons in Syria, with President Obama calling it a “red line.”

Hagel said that U.S. intelligence agencies were still conducting an assessment and that there was no timeline for reaching a conclusion.

“This is serious business. You want to be as sure as you can be on these kind of things,” he said. “That’s not at all questioning other nations’ intelligence, but the United States relies on its own intelligence.”

The Israeli general, Itai Brun, chief of the research division of Israel’s army intelligence branch, said Tuesday, “To the best of our professional understanding, the [Syrian] regime used lethal chemical weapons against gunmen in a series of incidents in recent months.”

Brun did not present evidence but said photographs showed victims “foaming at the mouth.” The second Israeli official, speaking on the condition of anonymity to discuss sensitive intelligence, said “dozens” were killed in five attacks in which a “sarin-type” nerve agent was dispersed.

Israeli officials said they have shared their findings with the U.S. government. U.S. officials acknowledged that Israeli and U.S. intelligence agencies have remained in close contact on the issue.

During his stop in Cairo, Hagel said he also discussed the Syrian conflict, among other issues, with Egyptian President Mohamed Morsi and Egyptian military leaders.

In Syria on Wednesday, forces loyal to President Bashar al-Assad seized a strategic town east of Damascus after more than 37 days of fighting in which rebels had accused the government of twice using chemical weapons, Reuters news service reported, citing activists and fighters. The capture of Otaiba severed a key rebel supply line, a spokesman said.

Separately, activists and state media said the 1,000-year-old minaret of Aleppo’s Umayyad Mosque had collapsed amid fighting between rebels and government forces. Aleppo’s Old City, where the mosque stands, is a U.N. world heritage site.