US Secretary of State Rex Tillerson has said President Donald Trump not discuss "sources, methods or military operations" in his meeting with Russian Foreign Minister Sergei Lavrov.
The statement by Mr Tillerson comes after The Washington Post reported that Mr Trump disclosed highly classified information to the Russian foreign minister during their meeting last week.
"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. During that exchange the nature of specific threats were discussed, but they did not discuss sources, methods or military operations," Mr Tillerson said.
The alleged disclosure potentially jeopardised a source of intelligence about the self-proclaimed Islamic State group, according to the report which cites current and former US officials.
The newspaper said the information Mr Trump relayed to Russian Foreign Minister Sergei Lavrov and Russian Ambassador Sergei Kislyak had been provided by a US partner through a highly sensitive intelligence-sharing arrangement.
The partner had not given the US permission to share the material with Russia, and Mr Trump's decision to do so risks cooperation from an ally that has access to the inner workings of IS, the Post said, citing the unnamed officials.
During his Oval Office meeting with Mr Lavrov and Mr Kislyak, Mr Trump went off-script and began describing details about an IS threat related to the use of laptop computers on aircraft, the officials told the Post.
While discussing classified matters with an adversary would be illegal for most people, the President has broad authority to declassify government secrets, making it unlikely that Mr Trump's disclosures broke the law, the Post said.
Mr Trump's meeting with the Russian pair at the White House came a day after he fired FBI Director James Comey, who was leading the agency's investigation into possible links between Mr Trump's presidential campaign and Russia.
Asked about the disclosures, Mr Trump's national security adviser, H R McMaster, who participated in the meeting, said no intelligence sources or methods were discussed that were not already known publicly, the Post reported.
Asked by Reuters about the story, Mr McMaster declined comment.
US officials have told Reuters that US agencies are in the process of drawing up plans to expand a ban on passenger scarrying laptop computers onto US-bound flights from severalcountries on conflict zones due to new intelligence about how militant groups are refining techniques for installing bombs in laptops.
So serious are assessments of the increased threat that the US is considering banning passengers from several European countries from carrying laptops in a cabin on US-bound flights.
The US has consulted about the intelligence with allied governments and airlines.
