Kushner and Flynn met with Russian ambassador in December

WASHINGTON — Michael Flynn, then Donald Trump's incoming national security adviser, had a previously undisclosed meeting with the Russian ambassador in December to "establish a line of communication" between the new administration and the Russian government, the White House said Thursday.

Jared Kushner, Trump's son-in-law and now a senior adviser, also participated in the meeting at Trump Tower with Flynn and Sergey I. Kislyak, the Russian ambassador. But among Trump's inner circle, it is Flynn who appears to have been the main interlocutor with the Russian envoy — the two were in contact during the campaign and the transition, Kislyak and current and former U.S. officials have said.

But the extent and frequency of their contacts remains unclear, and the disclosure of the meeting at Trump Tower adds to the emerging picture of how the relationship between Trump's incoming team and Moscow was evolving to include some of the president-elect's most trusted advisers.

The White House has repeatedly sought to play down any connections with Kislyak. Attorney General Jeff Sessions acknowledged this week that he had met twice with him during the campaign, despite previous denials.

The New Yorker reported this week that Kushner had met with Kislyak at Trump Tower in December. Hope Hicks, a White House spokeswoman, confirmed Thursday that Flynn was also at the meeting in response to questions from a New York Times reporter.

It is common and not improper for transition officials to meet with foreign officials. But all meetings between Trump associates and Russians are now significant as the FBI investigates Russian interference in the U.S. election and whether anyone close to Trump's campaign was involved.

[Obama aides left trail of intelligence on Trump associates and Russia for investigators]

The meeting in December came at a crucial time, just as the Obama White House was preparing to sanction Russia and publicly make its case that Moscow had interfered with the 2016 election.

What is becoming clear is that the incoming Trump administration was simultaneously striking a conciliatory pose toward Moscow in a series of meetings and phone calls involving Kislyak.

"They generally discussed the relationship and it made sense to establish a line of communication," she said. "Jared has had meetings with many other foreign countries and representatives — as many as two dozen other foreign countries' leaders and representatives."

The Trump Tower meeting lasted 20 minutes, and Kushner has not met since with Kislyak, Hicks said.

When first asked in January about Flynn's contacts with Kislyak, the White House said that there had been only a text message and phone call between the men at the end of December, and that both came before the United States imposed sanctions. That was quickly contradicted by news reports.

Flynn's story then began changing, and the White House eventually acknowledged the two men had discussed the sanctions and how the two countries could move past the acrimony once Trump was in office.

U.S. officials have also said that there were multiple telephone calls between Flynn and Kislyak on Dec. 29, beginning shortly after Kislyak was summoned to the State Department and informed that, in retaliation for Russian election meddling, the United States was expelling 35 people suspected of being Russian intelligence operatives and imposing other sanctions.

Kislyak was irate and threatened a forceful Russian response, according to people familiar with the exchange. He then left the State Department and called Flynn, the first in a series of calls between the two in the 36 hours that followed.

U.S. intelligence agencies routinely wiretap the phones of Russian diplomats, and transcripts of the calls showed that Flynn urged the Russians not to respond, saying relations would improve once Trump was in office, according to the current and former officials.

Flynn's failure to fully disclose the nature of the calls with Kislyak ultimately cost him his job last month after a tumultuous 25 days as national security adviser.

[Who is Sergey Kislyak, and how did he become the hottest meeting ticket in Washington?]

The U.S. government has concluded that Russia intended, at least in part, to help elect Trump through a campaign of cyberattacks, propaganda and misinformation. The government has concluded that Russian operatives were behind the hacking of the Democratic National Committee and John Podesta, chairman of Hillary Clinton's presidential campaign.

Current and former U.S. officials have said that Flynn had contacts with Kislyak during the campaign. But few of the specifics of those contacts were known. The Russian ambassador has acknowledged that the two men had known each other since 2013 and were in contact during the campaign.

"It's something all diplomats do," Kislyak was quoted as saying by The Washington Post, though he refused to say what subjects he discussed with Flynn.