DONALD Trump reportedly revealed highly classified information to Russian diplomats during his meeting with them at the White House last week.
The Washington Post reports that Mr Trump jeopardised a critical source of US intelligence on the Islamic State by disclosing information that hadn't even been shared with America's allies.
"The information the President relayed had been provided through an intelligence-sharing arrangement considered so sensitive that details have been withheld from allies and tightly restricted even within the US government," the paper reports.
The source in question, which is reportedly one of America's foreign allies, has access to the "inner workings" of ISIS and had provided intelligence on one of the group's plots. Mr Trump's decision to share that intel without the ally's permission could stop it from co-operating in the future.
A US official told the Washington Post Mr Trump had "revealed more information to the Russian ambassador than we have shared with our own allies".
Senior White House officials promptly contacted the CIA and NSA to try to contain the fallout.
Since the Washington Post story broke, the administration has firmly denied it, though both the New York Times CNN and Buzzfeed claim to have independently confirmed the details.
"This story is false. The President only discussed the common threats that both countries face," said Dina Powell, the Deputy National Security Adviser.
"At no time were any intelligence sources or methods discussed and no military operations were disclosed that were not already known publicly," said National Security Adviser H.R. McMaster. "The story that came out tonight, as reported, is false. I was in the room, it didn't happen."
The New York Times reports Mr Trump discussed the intelligence itself, not the source that collected it or the methods used.
However there is a fear is that Russia could use the information provided by Mr Trump to determine the source.
"Do not ask me about how this looks. We all know how this looks," a White House aide told The Daily Beast, as senior staff reportedly huddled behind the scenes, devising a sustained response to the story.
CHARGES OF HYPOCRISY
Mr Trump was extremely critical of his opponent in last year's election, Hillary Clinton, for her mishandling of classified information.
He repeatedly instigated chants of "lock her up" from crowds at his campaign rallies, and during one of the official debates, he told Ms Clinton to her face that she would "be in jail" if he were president.
Here are a couple of Mr Trump's tweets on the matter.
Crooked Hillary Clinton and her team "were extremely careless in their handling of very sensitive, highly classified information." Not fit!— Donald J. Trump (@realDonaldTrump) July 6, 2016
The real scandal here is that classified information is illegally given out by "intelligence" like candy. Very un-American!— Donald J. Trump (@realDonaldTrump) February 15, 2017
Since his inauguration, the President has urged America's intelligence agencies to downplay their investigation into Russia's meddling in the election and instead focus on hunting down leakers of classified information within the government.
"The real story that Congress, the FBI and all others should be looking into is the leaking of classified information. Must find the leaker now!" he said in March.
It should be noted that the President has the authority to declassify intelligence, though it's unclear whether Mr Trump actually knew what he was doing during his meeting with the Russians.
Intelligence experts are concerned about the President's handling of sensitive information. Here, for instance, is what former CIA Deputy Director Michael Morell told CBS after the story broke.
"This is highly damaging for two reasons. First, the Russians will undoubtedly try to figure out the source or the method of this information to make sure that it is not also collecting on their activities in Syria - and in trying to do that they could well disrupt the source.
"The second damage is that third countries who provide the United States with intelligence information will now have pause to do so if the United States is sharing such information with the Russians without their permission."
Other reactions to the news have been more strident, to say the least.
If Hillary Clinton leaked classified info to a Russian spook/diplomat, Republicans would rightly be drafting Articles of Impeachment N-O-W.— Ana Navarro (@ananavarro) May 15, 2017
For a President who complains so much about leaks, this is stunning https://t.co/H6lJvBY2Fm— Tammy Duckworth (@SenDuckworth) May 15, 2017
Where are all those folks who chanted "lock her up"?https://t.co/wVbxNUv4HX— Gerry Connolly (@GerryConnolly) May 15, 2017
1. Call Russia investigation a hoax. 2. Fire lead investigator. 3. Spill highly classified info to Russians. Time for independent counsel.— Rep. Ted Deutch (@RepTedDeutch) May 15, 2017
"This is quite literally the sum of all fears," Thomas Wright, a US foreign policy expert, told the Washington Post. "We have heard that Trump is normalising. It is nonsense. There are some sensible people around him working around the clock to avert catastrophe but ultimately he is in charge and he will do what he wants, no matter how mad. We are blind and dancing on the precipice."
Legal expert Alan Dershowitz went even further during an interview with CNN.
"This is the most serious charge ever made against a sitting president of the United States. Let's not minimise it," Mr Dershowitz said. "Something has to be done."
As the CNN host Erin Burnett pointed out, other presidents have been accused of criminal conduct - but Mr Dershowitz stood by his statement.
Last week's Oval Office meeting with Russian Ambassador Sergei Kislyak and Foreign Minister Sergei Lavrov was already controversial. Mr Trump barred US media from the meeting, but allowed Russian media inside with their equipment, leading to fears the White House's security had been compromised.
This news also comes just a week after Mr Trump abruptly fired his FBI Director, James Comey, who was overseeing an investigation into Russia's interefence in the 2016 presidential election - and potential collusion between Russia and members of Mr Trump's campaign team.
The White House initially said Mr Comey had been fired for his handling of Hillary Clinton's email scandal, but as that story collapsed, Mr Trump admitted the Russia investigation was a factor.
"I was going to fire Comey. Regardless of the recommendation (from Deputy Attorney General Rod Rosenstein) I was going to fire Comey," Mr Trump told NBC's Lester Holt.
"He's a showboat, he's a grandstander, the FBI has been in turmoil," Mr Trump added. "You know that, I know that. Everybody knows that. You take a look at the FBI a year ago, it was in virtual turmoil, less than a year ago. It hasn't recovered from that."
Mr Trump said Mr Rosenstein's memo, which focused on the Clinton saga, was not the main reason for the sacking - and implied the investigation into Russia was.
"When I decided to do it, I said to myself ... this Russia thing with Trump and Russia is a made up story," Mr Trump said.
The President also threatened Mr Comey on Twitter, implying their private conversations had been recorded and warning him not to leak to the press.
James Comey better hope that there are no "tapes" of our conversations before he starts leaking to the press!— Donald J. Trump (@realDonaldTrump) May 12, 2017
If Mr Trump's Oval Office discussions have indeed been recorded, that means his disclosure of classified information to the Russians could be on tape as well. So that is one tweet the President might live to regret.
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