WASHINGTON - US President Donald Trump defended wanting to share terrorism intelligence with Russian officials in a White House meeting last week, saying he has the "absolute right" to do so.

"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," he said in a series of tweets on Tuesday (May 16).

"Humanitarian reasons, plus I want Russia to greatly step up their fight against ISIS & terrorism," Mr Trump remarked after his top foreign-policy advisers raced to contain political damage from a Washington Post report that the president revealed to Russia's foreign minister and ambassador highly classified information from a US intelligence partner about an Islamic State in Iraq and Syria (ISIS) plot.

Mr Trump was already fending off questions about his firing of FBI Director James Comey amid an investigation of possible collusion by Trump associates in Russian interference with the US election.

The "story that came out tonight as reported is false", White House National Security Adviser H.R. McMaster said on Monday (May 15) at a hastily arranged appearance outside the White House. "At no time were intelligence sources or methods discussed, and the president did not disclose any military operations that were not already publicly known."

"I was in the room. It didn't happen," General McMaster said in a statement that lasted less than a minute. He left without taking questions.

According to the Washington Post, the intelligence involved information about an ISIS plot to use laptop computers as possible weapons aboard commercial aircraft and had been provided by a US ally with access to the inner workings of the terrorist group.

While Mr Trump didn't reveal the specific methods that developed the information or sources, he described elements of a specific plot and the city in ISIS' territory where the threat was detected, the Post said.

That specific information could be enough to let the Russians identify the source and method, according to one intelligence official cited by the Post.

The newspaper cited unnamed current and former US officials with knowledge of the exchange, who said they recognised that it jeopardised intelligence capabilities.

The Post said homeland security and counter-terrorism adviser Thomas Bossert called the directors of the CIA and the National Security Agency afterward. One of his subordinates called for that portion of the discussion stricken from internal memos and circulation of a transcript limited to prevent sensitive details from being further distributed, the newspaper said.

The intelligence was held by the US at one of the highest classification levels that would typically prevent it from being shared even with allies, according to the Post.

The Kremlin on Tuesday denied the report that Mr Trump shared secrets at his White House meeting with Russian Foreign Minister Sergei Lavrov and Ambassador Sergey Kislyak.

The denial came after Russian Foreign Ministry spokeswoman Maria Zakharova ridiculed the Post report on Tuesday, writing on Facebook that American newspapers "can be used for other things but there's no need to read them - in recent times it's not only harmful but dangerous".

"We don't want anything to do with this nonsense," Kremlin spokesman Dmitry Peskov told reporters on a conference call. "It's complete nonsense."

The revelation may have additional peril for Mr Trump because during his campaign against Democrat Hillary Clinton last year, he repeatedly assailed her "careless" use of a private email system while she was secretary of state, a practice he argued could have exposed classified information.

He claimed it made her unfit for the presidency. Surrogates at his campaign rallies led chants of "lock her up!"

Top lawmakers of both parties, while saying they weren't able to comment on the substance of the report, said it raised new questions about the administration.

"We have no way to know what was said, but protecting our nation's secrets is paramount," said Mr Doug Andres, a spokesman for House Speaker Paul Ryan. "The speaker hopes for a full explanation of the facts from the administration."

"The White House has got to do something soon to bring itself under control and in order," Republican Senator Bob Corker, the chairman of the Foreign Relations Committee, told reporters at the Capitol. "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."

Senator Jack Reed, the ranking Democrat on the Armed Services panel, said sharing information without the permission of a foreign intelligence partner "violates a cardinal rule" of dealing with friendly agencies.

"If it's accurate, it's disturbing because it's divulging information about operations in Syria which could be exploited not only by the Russians to interrupt intelligence operations that they feel are threatening to them," Mr Reed said.

The intelligence involved may be behind the US. announcement on March 21 that electronic devices larger than smartphones would be banned from cabins on flights originating from 10 airports in the Middle East and Africa. The Department of Homeland Security has been considering expanding the restriction to flights from Europe.

The president has broad authority to declassify information so it's not likely he broke the law, according to the Washington Post, even though he shared it with a US adversary.

"We certainly don't want any president to leak classified information but the president does have the right to do that, because he's commander-in-chief," Senator John McCain, an Arizona Republican, told reporters on Monday shortly after the news broke. "Any president needs to be careful" with classified information, he said.

US presidents in the past have either intentionally or inadvertently released classified information about surveillance capabilities and intelligence that was collected.

"Presidents have often revealed, on their own authority (and sometimes inadvertently), secrets about collection capabilities that the Intelligence Community would have preferred to have kept secret, because such exposure tends to make such collection more difficult," Mr Nicholas Dujmovic, a Catholic University of America professor in Washington who spent more than 25 years at the CIA, said in an e-mail.

President Richard Nixon mistakenly revealed US abilities to monitor Soviet and Chinese electronic transmissions in the Far East and President Jimmy Carter acknowledged for the first time that the US used satellites to collect overhead imagery, Mr Dujmovic said. President Ronald Reagan ordered the release of transcripts from the National Security Agency to show that the Soviet shootdown of KAL 007 in 1983 was deliberate, he added.

"Presidents can do this; in a sense, they 'own' US secrets," Mr Dujmovic said. "But in a larger sense, they are the custodians of the secrets that need to be kept for the sake of US national security, and what President Trump is alleged to have done goes beyond the pale. If the Post reporting is accurate, he revealed compartmented information on the spur of the moment, simply to impress his foreign guests. If true, the story will indeed harm relations with US allies who are our closest intelligence partners and will now be wary of sharing their best secrets with us."

Mr Trump met with Mr Lavrov and Mr Kislyak one day after firing Mr Comey, who was leading an investigation into possible collusion between Trump associates and Russian agents trying to interfere with the US presidential election.

Mr Trump's meeting with the Russian officials wasn't open to US media. Russia's state-owned Tass news service released photos of the meeting showing Mr Trump, Mr Lavrov and Mr Kislyak standing in the Oval Office, smiling at each other.

Mr Trump has denied any connection to Russia while also questioning the assessment of US intelligence agencies that the government in Moscow directed a campaign of hacking and disinformation to disrupt the election.

Some Democrats said the latest incident is indicative of lax leadership in the Trump White House.

"This president is sitting in the Oval Office and making snap decisions that are not based on the advice of his people that we see the White House trying to work out in the days that follow," Representative Jim Himes, a Connecticut Democrat who is a member of the House intelligence committee that is also investigating Russian meddling in the election, told CNN on Tuesday.