John Kerry denies ever having discussed Israeli strikes in Syria with Iran’s foreign minister.

John Kerry, a former secretary of state, said on Monday that he had never discussed covert Israeli airstrikes in Syria with Iran’s foreign minister, Mohammad Javad Zarif, contrary to Mr. Zarif’s claim in a leaked conversation.

Mr. Zarif and Mr. Kerry spoke constantly when the two were negotiating the 2015 Iran nuclear deal. The Iranian foreign minister said in the recording, reported by The New York Times on Sunday, that Mr. Kerry had informed him that Israel had attacked Iranian interests in Syria at least 200 times.

The claim sparked a furor on Monday among conservatives who accused Mr. Kerry, who was secretary of state in the Obama administration and now serves as President Biden’s climate envoy, of betraying Israeli secrets.

But in a tweet on Monday evening, Mr. Kerry denied the assertion and pointed to reports long in the public domain about Israeli strikes on Iranian assets in Syria.

“I can tell you that this story and these allegations are unequivocally false. This never happened — either when I was Secretary of State or since,” Mr. Kerry wrote.

Mr. Kerry’s denial came after multiple attacks from prominent Republicans. Senator Ted Cruz, Republican of Texas, said that, if real, the remarks would amount to “catastrophic and disqualifying recklessness.”

Senator Dan Sullivan, Republican of Alaska and a former State Department official under President George W. Bush, called in a speech on the Senate floor for Mr. Kerry to resign, saying he was “astonished” that Mr. Kerry “would reveal the secrets of one of our most important and enduring allies in the region to an avowed enemy, the largest state sponsor of terrorism.”