Trumps candidacy. Details of the reports began circulating in the fall and were widely known among journalists and politicians in Washington. The two-page summary, first reported by CNN, was presented as an appendix to the intelligence agencies report on Russian hacking efforts during the election, the officials said.

The material was not corroborated, and The New York Times has not been able to confirm the claims. But intelligence agencies considered it so potentially explosive that they decided Mr. Obama, Mr. Trump and congressional leaders needed to be told about it and informed that the agencies were actively investigating it.

Intelligence officials were concerned that the information would leak before they informed Mr. Trump of its existence, said the officials, who spoke on the condition of anonymity because they were not authorized to speak about it publicly. The author of the memos is Christopher Steele, a former British intelligence officer with MI-6, who once served in Moscow.

After Mr. Steele retired in 2009, he founded a private firm called Orbis Business Intelligence in London. - 2018 ©