National security adviser General Michael Flynn (L) arrives to deliver a statement next to Press Secretary Sean Spicer during the daily briefing at the White House in Washington U.S., February 1, 2017.

A U.S. intelligence official briefed on the matter confirmed to NBC News that National Security Advisor Mike Flynn discussed sanctions with the Russian ambassador before Flynn took office, contrary to denials from Vice President Mike Pence, White House spokesman Sean Spicer, and others.

The official said he was told there was no quid pro quo and that there has been no finding inside the government that Flynn did anything illegal.

But he said he was surprised when Flynn initially denied to the Washington Post, which first reported this story, that he discussed sanctions on Russia with the ambassador. His spokesman later said he didn't recall and it was possible he did, according to the Post.

An administration official told the Post that Pence based his comments denying that Flynn had discussed sanctions on what Flynn told him.

Flynn's contact with Sergey Kislyak, Russia's ambassador to the U.S., were seen by critics as a potential violation of the law. The Obama administration imposed sanctions before leaving office to punish Russia for using hackers to interfere in the U.S. presidential election. As a candidate and as president-elect, President Trump repeatedly expressed doubt about whether Russia had interfered, despite the unanimous opinion of the intelligence community.

Flynn spoke to Kislyak on Dec. 29, the same day the sanctions were announced. Prior to President Trump's inauguration, members of the Trump transition team acknowledged the contact but said sanctions weren't discussed

The Post, which based its new reporting on nine sources, said Flynn twice denied on Wednesday that he discussed sanctions with Kislyak, but then changed his answer on Thursday.

Russian officials did not immediately respond to a request for comment.