WASHINGTON, United States (AFP) — Embattled US President Donald Trump insisted Tuesday he had the right to share “facts” with Russia, one day after bombshell allegations that he divulged highly classified intelligence to Russian diplomats in the Oval Office.

According to an explosive report from the Washington Post, Trump revealed highly classified information on the Islamic State group during a meeting last week with Russian Foreign Minister Sergei Lavrov and Moscow’s man in Washington Sergey Kislyak.

In a shock twist, the information reportedly came from a US ally who had not authorized Washington to share it with Moscow, a potential blow to intelligence relationships based on trust that secrets will be kept.

“As President I wanted to share with Russia (at an openly scheduled W.H. meeting) which I have the absolute right to do, facts pertaining to terrorism and airline flight safety,” Trump pushed back in an early morning tweet.

Trump wrote that he was motivated by “humanitarian reasons, plus I want Russia to greatly step up their fight against ISIS & terrorism.”

The US leader’s disclosure of classified information did not break the law, according to the national security blog Lawfare, but such revelations could expose sources and methods and “substantially harm” US intelligence gathering partnerships with foreign governments.

“This is perhaps the gravest allegation of presidential misconduct in the scandal-ridden four months of the Trump administration,” the blog said. “This story is likely to be immensely consequential.”

National Security Advisor HR McMaster denied the president revealed “intelligence sources or methods,” but acknowledged that Trump and Lavrov “reviewed a range of common threats to our two countries, including threats to civil aviation.”

Kremlin spokesman Dmitry Peskov on Tuesday dubbed the news “nonsense,” saying it was not worth confirming or denying.

The Post, citing unnamed officials, said Trump went off script during the meeting, describing details about an Islamic State terror threat related to the use of laptop computers on airplanes, revealing the city where the information was gathered.

The Trump administration recently barred the use of laptops in the passenger cabin from several countries in the Middle East and is mulling the expansion of that ban to cover jets originating in Europe.

“There’s nothing that the president takes more seriously than the security of the American people. The story that came out tonight as reported is false,” McMaster said without elaborating on which elements were wrong.

“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. I was in the room. It didn’t happen.”

McMaster earlier refused to answer questions to a group of journalists gathered in the West Wing, saying “this is the last place I wanted to be” before leaving.

The revelations are the latest in a wave of crises to hit the White House, which late Monday was in a state of shock, with aides frantically trying to put out the fire and determine the source of such damaging leaks.

“I have been asking Director Comey & others, from the beginning of my administration, to find the LEAKERS in the intelligence community,” Trump tweeted Tuesday.

Since coming to office in January, Trump has lurched from crisis to crisis, lampooning the intelligence services, law enforcement and the media along the way.

Last week, Trump threw his administration into turmoil by taking the rare step of firing his FBI director James Comey.

Comey had been overseeing investigations into possible Trump campaign collusion with Russia to skew the 2016 election.

Trump’s meeting with top Russian diplomats came one day after Comey’s firing.

But political and legal experts said this latest misstep is among the most egregious so far of Trump’s presidency.

For Trump’s already weary allies in Congress, the latest crisis brought more headaches and demanded yet more explanation from an administration that is struggling to leave its legislative mark.

“The White House has got to do something soon to bring itself under control and in order. It’s got to happen,” said Republican Senator Bob Corker.

“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,” Corker said.

Meanwhile, top Senate Democrat Chuck Schumer accused Trump of potentially putting American lives at risk.

“If the report is true, it is 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,” the New York senator said.

“The president owes the intelligence community, the American people and Congress a full explanation.”