US President Donald Trump divulged highly classified information about ISIS to Russian Foreign Minister Sergei Lavrov when the two met at the White House last week, according to official sources.
The information had been provided by a US ally who hadn't given Washington permission to share it with Russia, the Washington Post reported.
The Trump administration has dismissed the report, calling it "false."
Of Trump, Russia and the "alleged" ties!
Trump went "off-script," gave information to Russian diplomats
The President reportedly went "off script" while discussing an ISIS plot with Lavrov and Russian ambassador Sergei Kislyak.
He provided intelligence details reportedly connected to an ISIS plot involving the use of laptops on board passenger planes.
The information, which came from a US ally, was too sensitive to even share with other allies.
The information's disclosure could put an intelligence source at risk.
Trump could face swift backlash over reported information slip
The reports come days after Trump fired FBI director James Comey, who was investigating alleged collusion between the Trump campaign and Russia, and Moscow's election meddling. Trump has denied both allegations.
The reports will flame allegations by Trump critics that he is undisciplined and inexperienced to handle foreign policy matters.
The reports could also exacerbate Trump's ongoing feud with the US intelligence community.
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Trump's team tried to "contain the damage"
Trump's aides who were present at the meeting realized the mistake and scrambled to "contain the damage" by informing various US intelligence agencies such as the CIA, FBI and NSA.
NSA denies reports
NSA - "I was in the room. It didn't happen"
"At no time were any intelligence sources or methods discussed and no military operations were disclosed that were not already known publicly," he added.
He denied reports of Trump's information slip saying: "I was in the room. It didn't happen."
Secretary of state clarifies what was discussed in meeting
"During President Trump's meeting with Foreign Minister Lavrov, a broad range of subjects were discussed, among which were common efforts and threats regarding counter-terrorism," said US Secretary of State Rex Tillerson.
"During that exchange, the nature of specific threats were discussed, but they did not discuss sources, methods or military operations."
Democrat leader says reports "very disturbing" if true
Senate Democratic leader Chuck Schumer said the reports, if true, are "very disturbing."
"Revealing classified information at this level is extremely dangerous and puts at risk the lives of Americans and those who gather intelligence for our country," he added.
Schumer said: "The President owes the intelligence community, the American people, and Congress a full explanation."