The source of highly classified intelligence that President Trump discussed with Russia's foreign minister and ambassador is considered to be the best source for information regarding external plots by ISIS, according to a new report.

The Wall Street Journal, citing intelligence officials, reports the intelligence came from an Israeli source that is key to tracking ISIS’s plans to place bombs on commercial flights.

The Journal adds that intelligence officials disagree over how much harm Trump caused by discussing the intelligence with Russian officials last week. One official said there’s now a greater risk that the source could be comprised in some way, but another said that Russia wouldn’t be able to identify the source based on what Trump said.

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National security adviser H.R. McMaster said on Tuesday that Trump did not jeopardize intelligence assets by discussing the information with Russian officials, adding that Trump didn’t know where the intelligence came from.

"The president wasn’t even aware of where this information came from,” he said. “He wasn’t briefed on the source."

Critics worry that Trump’s discussion of the classified information with Russian officials could jeopardize valuable intelligence relationships between the U.S. and foreign countries. The Associated Press reported on Tuesday that a European intelligence official warned that his country may stop sharing information with the U.S. as a result of Trump’s disclosure.

Trump has defended sharing the information with Russia, saying he has the “absolute right” to do so.

As President I wanted to share with Russia (at an openly scheduled W.H. meeting) which I have the absolute right to do, facts pertaining.... — Donald J. Trump (@realDonaldTrump) May 16, 2017