The president could have hampered the U.S. response to ISIS, security experts say.

President Donald Trump’s allegedly loose lips with the Russians could have caused serious damage to U.S. efforts to counter the Islamic State, intelligence experts and former government security officials of both parties said Monday night.

And if Monday’s Washington Post story is true, they said, it raises new questions about the president’s preparation to handle the highly sensitive information that’s an inherent part of his job.

“If true, it is another indication that you cannot possibly control this guy,” Wayne White, a senior intelligence official at the State Department during the George W. Bush administration, told POLITICO. “There are red lines that even presidents are not supposed to be crossing. He has to be protecting his own assets. It is really frightening for our people, especially the people who managed the relationship in getting the information.”

“This is really the nightmare scenario for the intelligence community,” Ned Price, a former CIA officer and member of the National Security Council staff under former President Barack Obama, told MSNBC.

Eliot Cohen, another Bush-era State Department official and professor of strategic studies at Johns Hopkins School of International Studies, called the report “appalling.”

“If accidental, it would be a firing offense for anyone else,” Cohen tweeted. “If deliberate, it would be treason.”

The Post’s report, which caused an immediate furor, said Trump shared “highly classified information” in an Oval Office meeting last week with Russian Foreign Minister Sergey Lavrov and ambassador Sergey Kislyak. It added that the information concerned an “Islamic State terrorist threat related to the use of laptop computers on aircraft,” and had been obtained “through an intelligence-sharing arrangement considered so sensitive that details have been withheld from allies and tightly restricted even within the U.S. government.”

The Trump administration immediately rejected the report as untrue, even as other news outlets such as The New York Times confirmed it.

“The story that came out tonight, as reported, is false,” Lt. Gen. H.R. McMaster, Trump’s national security adviser, told reporters at the White House, without taking questions.

“The president and foreign minister reviewed a range of common threats to our two countries including threats to civil aviation,” McMaster added. “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. Two other senior officials who were present, including the secretary of State, remember the meeting the same way, and have said so. Their on the record accounts should outweigh those of anonymous sources. And I was in the room, it didn’t happen.”

The Post story asserts, however, that NSC officials were concerned enough about what Trump said that they contacted U.S. intelligence agencies about it.

Even if Trump shared only minimal information that was considered highly classified, a number of experts said, it is a stark reminder of the lingering concerns many intelligence professionals have about entrusting sensitive national security information to a president who has dismissed their expertise and has no prior experience in government or the military.

The president is authorized by law to make public any and all classified information he or she sees fit — so anything that Trump may have shared of a classified nature was his prerogative.

But that doesn’t mean doing so doesn’t have the same repercussions as if someone purposely leaked classified information to cause damage, specialists said.

“It is not a legal issue. It is a question of competence and national security awareness. If the story is accurate the president fell short in those vital areas,” said Steve Aftergood, a specialist on government secrecy at the Federation of American Scientists. “At face value it appears that the president behaved recklessly and thoughtlessly and may have compromised a vital intelligence source.”

Bill Leonard, who in 2007 oversaw the government’s classification system as director of the Information Security Oversight Office, said Trump probably didn’t realize what he was sharing could be damaging to intelligence activities.

“Individuals when provided access to sensitive intelligence information don’t realize it is not just what the info is but how it is collected,” he said in an interview. “It may not be readily apparent to people not familiar with intelligence. But the mere concept of the information may be revealing.”

For example, “If someone revealed that [Russian President Vladimir] Putin had eggs and bacon for breakfast, that seems innocuous. How the heck do we know what he had for breakfast? It is potentially source revealing.”

The fallout among allied spy agencies overseas is also likely to be immediate, predicted White, who has briefed dozens of allied leaders and officials on security matters.

“It probably confirms to them that he is a loose cannon,” he said. “They might all start looking into how much they might want to give the United States of a sensitive nature, particularly if this reveals sources and methods.”

In Aftergood’s view the Post report also underscores how much tension exists within Trump’s White House.

“I’m mostly struck at the antagonism toward the president that the story represents,” Aftergood said.

But it almost assuredly not going to over well with U.S. intelligence agencies, the experts said.

“This is the kind of thing that feeds a cycle of hostility and retribution,” Aftergood said. “I’m waiting to see what the president tweets about it. It both reflects and reinforces growing tension between the White House and the intelligence community.”