Last week, during a meeting with the Russian foreign minister and ambassador, President Donald Trump revealed highly classified intelligence to Russia, according to a U.S. government official.

Officials said that Trump bragged to Sergey V. Lavrov, the Russian foreign minister, and Sergey I. Kislyak, the Russian ambassador to the United States, about how intelligence was gathered on a plot by the Islamic State.

The problem is not necessarily the declassification of information, since the president has the ability and authority to declassify almost anything, but the fact that the information on the plot was gathered by a U.S. ally in the Middle East that so closely guards its intelligence gathering secrets that the information shared on how the plot was uncovered was not shared widely in the government or passed on to other allies.

By sharing the information, Trump has broken with espionage etiquette, which could jeopardize the relationships, especially because this ally has reportedly warned the United States that it would not share information with the United States if that information became too widely known.

There is a real possibility that Trump and others in the room simply did not realize the classified nature of the information being shared, as it wasn’t until notes on the meeting were reviewed by National Security Council officials that the information was flagged.

After the Washington Post first reported Trump’s disclosure, White House officials denied that Trump shared the details of the intelligence but did not say whether or not he had spoken about the plot itself.

“I was in the room — it didn’t happen,” Lt. Gen. H. R. McMaster, Mr. Trump’s national security adviser, said on Monday.

“At no time — at no time — were intelligence sources or methods discussed, and the president did not disclose any military operations that were not already publicly known,” General McMaster said.

The worry is, however, that the Russians will be able to figure out where the intelligence came from based on what Trump did share with them, even if specifics were not fully discussed.

Even members of Congress criticized the breach in intelligence protocol.

“The White House has got to do something soon to bring itself under control and in order,” Senator Bob Corker, Republican of Tennessee and the chairman of the Foreign Relations Committee, told reporters at the Capitol, adding, “It’s got to happen.”

“To compromise a source is something that you just don’t do, and that’s why we keep the information that we get from intelligence sources so close as to prevent that from happening.”