President Donald Trump revealed highly classified information about so-called Islamic State (IS) to Russia’s foreign minister, officials have told US media.
The information came from a partner of the US which had not given the US permission to share it with Russia, says the Washington Post.
It happened when Mr Trump met Sergei Lavrov in the Oval Office last week, says the paper.
But a senior security official has said the report is not true.
“This story is false,” said Dina Powell, deputy national security adviser for strategy, who was in the meeting. “The president only discussed the common threats that both countries faced.”
Mr Trump’s National Security Advisor, Gen HR McMaster, also said the story was false.
The Trump campaign’s alleged links to Moscow have dogged his presidency, and are part of several investigations.
But the president has dismissed it as “fake news”.
During the election campaign, Mr Trump repeatedly criticised his Democratic opponent, Hillary Clinton, for how she handled sensitive material.
