U.S. President Donald Trump meets with Russian Foreign Minister Sergey Lavrov, left, next to Russian Ambassador to the U.S. Sergei Kislyak at the White House in Washington, Wednesday, May 10, 2017. Russian Foreign Ministry Photo via AP President Donald Trump last week shared highly classified intelligence with the Russian foreign minister and ambassador in an Oval Office meeting that was so under wraps that American allies were not aware of the information, The Washington Post reported Monday.

Current and former anonymous US officials told The Post that Trump's disclosures to Russian Foreign Minister Sergey Lavrov and Ambassador Sergey Kislyak jeopardized a key source of intelligence about the Islamic State terror group, as the source had not given the US permission to share the intelligence with Russia.

Officials told The Post that Trump's disclosure risked the cooperation of an ally that has access inside of ISIS. Matthew Rosenberg of The New York Times told CNN on Monday that the intel came from a close "Middle Eastern ally."

Trump "revealed more information to the Russian ambassador than we have shared with our own allies," one official said. The incident happened last Wednesday, one day after Trump fired FBI Director James Comey.

The FBI is investigating any potential collusion between the Trump campaign and Russian officials to swing the 2016 election as a part of a counterintelligence investigation into Russian interference in November's presidential election.

Trump welcomed Kislyak and Lavrov to the Oval Office without any American press present to document the meeting. Kislyak is at the center of a number of Russia-related controversies, including from his conversations with ousted national-security adviser Michael Flynn and Attorney General Jeff Sessions.

Russian photographers were allowed in and subsequently posted photos of Trump looking jubilant with Lavrov and Kislyak, a move that upset some within the White House.

During the meeting with the two Russian diplomats, Trump went off script and began to tell them about an ISIS plot related to the recently implemented laptop ban on some international flights, officials told The Post.

The disclosures were likely not illegal, The Post wrote, because of the president's broad authorities on declassification.

"The president and the foreign minister reviewed common threats from terrorist organizations to include threats to aviation," H.R. McMaster, Trump's national security adviser, who was in the meeting, told The Post. "At no time were any intelligence sources or methods discussed and no military operations were disclosed that were not already known publicly."

In a similarly worded statement, Secretary of State Rex Tillerson said a "broad range of subjects were discussed, among which were common efforts and threats regarding counter-terrorism."

"During that exchange, the nature of specific threats were discussed, but they did not discuss sources, methods, or military operations," Tillerson added.

And Deputy National Security Adviser Dina Powell said the "story is false."

"The president only discussed the common threats that both countries faced," she said.

Other officials wondered whether Trump understood the difference between classified and declassified intelligence.

"It is all kind of shocking," a former senior US official close to current administration officials told The Post. "Trump seems to be very reckless, and doesn’t grasp the gravity of the things he’s dealing with, especially when it comes to intelligence and national security. And it’s all clouded because of this problem he has with Russia."

Republican Sen. Bob Corker of Tennessee, chair of the Senate Foreign Relations Committee, told Bloomberg that the Trump White House "has got to do something soon to bring itself under control and in order. It's got to happen."

"Obviously they're in a downward spiral right now and they've got to figure out a way to come to grips with all that's happening," he added.

And Republican Sen. John McCain of Arizona told CNN that "if" the Post story "is true, I would say it's disturbing."

In that meeting with Lavrov and Kislyak, Trump said to the Russians, "I get great intel. I have people brief me on great intel every day," an official with knowledge of the exchange told The Post.

Trump discussed aspects of the ISIS threat, including the city where the ploy was detected. But he did not reveal the intelligence gathering method.

"If that partner learned we’d given this to Russia without their knowledge or asking first that is a blow to that relationship," a US official told The Post.

BuzzFeed confirmed the Post report shortly after on Monday, citing two anonymous US officials who were briefed on the intelligence disclosures last week.

"It's far worse than what has already been reported," one of the officials told BuzzFeed.