"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 wrote. "Humanitarian reasons, plus I want Russia to greatly step up their fight against ISIS & terrorism."
The Washington Post first reported the news that in a May 10 meeting, Trump revealed "highly classified" information to the Russian foreign minister and Russian ambassador.
Members of the U.S. press were not allowed into the meeting, but the Russians' "official photographer" took photos that were posted on social media and distributed to wire service, Politico reported. An official said the official White House photographer also was there, Politico reported.
In a meeting with Russian Foreign Minister Sergei Lavrov and Russian Ambassador Sergey Kislyak, Trump jeopardized a source of intelligence on the Islamic State group, according to the paper.
Trump has the power to declassify anything, but sharing information without permission of the ally who provided it represents "a major breach of espionage etiquette, and could jeopardize a crucial intelligence-sharing relationship," according to The New York Times.
National Security Adviser H.R. McMaster says no intelligence sources or methods were discussed and no military operations were disclosed that were not already known publicly.
– The Associated Press contributed to this report.