WASHINGTON — Weeks before President Trump’s inauguration, his national security adviser, Michael T. Flynn, discussed American sanctions against Russia, as well as areas of possible cooperation, with that country’s ambassador to the United States, according to current and former American officials.
Throughout the discussions, the message Mr. Flynn conveyed to the ambassador, Sergey I. Kislyak — that the Obama administration was Moscow’s adversary and that relations with Russia would change under Mr. Trump — was unambiguous and highly inappropriate, the officials said.
The accounts of the conversations raise the prospect that Mr. Flynn violated a law against private citizens’ engaging in diplomacy, and directly contradict statements made by Trump advisers. They have said that Mr. Flynn spoke to Mr. Kislyak a few days after Christmas merely to arrange a phone call between President Vladimir V. Putin of Russia and Mr. Trump after the inauguration.
But current and former American officials said that conversation — which took place the day before the Obama administration imposed sanctions on Russia over accusations that it used cyberattacks to help sway the election in Mr. Trump’s favor — ranged far beyond the logistics of a post-inauguration phone call. And they said it was only one in a series of contacts between the two men that began before the election and also included talk of cooperating in the fight against the Islamic State, along with other issues.
The officials said that Mr. Flynn had never made explicit promises of sanctions relief, but that he had appeared to leave the impression it would be possible.
Mr. Flynn could not immediately be reached for comment about the converations, details of which were first reported by The Washington Post. Despite Mr. Flynn’s earlier denials, his spokesman told the Post that “while he had no recollection of discussing sanctions, he couldn’t be certain that the topic never came up.”
During the Christmas week conversation, he urged Mr. Kislyak to keep the Russian government from retaliating over the coming sanctions — it was an open secret in Washington that they were in the works — by telling him that whatever the Obama administration did could be undone, said the officials, who spoke on the condition of anonymity because they were discussing classified material.
Days before Mr. Trump’s inauguration, Vice President-elect Mike Pence also denied that Mr. Flynn had discussed sanctions with Mr. Kislyak. He said he had personally spoken to Mr. Flynn, who assured him that the conversation was an informal chat that began with Mr. Flynn extending Christmas wishes.
“They did not discuss anything having to do with the United States’ decision to expel diplomats or impose censure against Russia,” Mr. Pence said on the CBS News program “Face the Nation.”
Some officials regarded the conversation as a potential violation of the Logan Act, which prohibits private citizens from negotiating with foreign governments in disputes involving the American government, according to one current and one former American official familiar with the case.
Federal officials who have read the transcript of the call were surprised by Mr. Flynn’s comments, since he would have known that American eavesdroppers closely monitor such calls. They were even more surprised that Mr. Trump’s team publicly denied that the topics of conversation included sanctions.
The call is the latest example of how Mr. Trump’s advisers have come under scrutiny from American counterintelligence officials. The F.B.I. is also investigating Mr. Trump’s former campaign chairman, Paul Manafort; Carter Page, a businessman and former foreign policy adviser to the campaign; and Roger Stone, a longtime Republican operative.
Prosecutions in these types of cases are rare, and the law is murky, particularly around people involved in presidential transitions. The officials who had read the transcripts acknowledged that while the conversation warranted investigation, it was unlikely, by itself, to lead to charges against a sitting national security adviser.
But, at the very least, openly engaging in policy discussions with a foreign government during a presidential transition is a remarkable breach of protocol. The norm has been for the president-elect’s team to respect the sitting president, and to limit discussions with foreign governments to pleasantries. Any policy discussions, even with allies, would ordinarily be kept as vague as possible.
“It’s largely shunned, period. But one cannot rule it out with an ally like the U.K.,” said Derek Chollet, who was part of the Obama transition in 2008 and then served in senior roles at the State Department, White House and Pentagon.
“But it’s way out of bounds when the said country is an adversary, and one that has been judged to have meddled in the election,” he added. “It’s just hard to imagine anyone having a substantive discussion with an adversary, particularly if it’s about trying to be reassuring.”