Washington - Just six days into his presidency, Donald Trump was informed his national security adviser had misled his vice president about contacts with Russia. Trump kept his No 2 in the dark and waited nearly three weeks before ousting the aide, Michael Flynn, citing a slow but steady erosion of trust, White House officials say. Flynn was interviewed by the FBI about his telephone conversations with Russia's ambassador to the US, a sign his ties to Russia had caught the attention of law enforcement officials.Deeply frustratedBut in the White House's retelling of Flynn's stunning downfall, his error was not that he discussed US sanctions with the Russian before the inauguration — a potential violation of a rarely enforced law — but the fact that he denied it for weeks, apparently misleading Vice President Mike Pence and other senior Trump aides about the nature of the conversations. White House officials said they conducted a thorough review of Flynn's interactions, including transcripts of calls secretly recorded by US intelligence officials, but found nothing illegal.Pence, who had vouched for Flynn in a televised interview, is said to have been angry and deeply frustrated.And Trump lashed out at the news media on Wednesday, sending out a tweet berating some news organizations for focusing on "This Russian connection non-sense." In a post on his verified Twitter account, Trump said, "The fake news media is going crazy with their conspiracy theories and blind hatred." He added that the news reporting was "merely an attempt to cover-up the many mistakes made in Hillary Clinton's losing campaign."Trump also asserted in a tweet: "Information is being illegally given to the failing @nytimes & @washingtonpost by the intelligence community (NSA and FBI?). Just like Russia."Flynn, in an interview with The Daily Caller News Foundation, said on Monday "there were no lines crossed" in his conversations with Russian Ambassador Sergey Kislyak.The explanation of the episode left many questions unanswered, including why Trump didn't alert Pence to the matter and why Trump allowed Flynn to keep accessing classified information and taking part in the president's discussions with world leaders up until the day he was fired.Friendly postureWhite House officials also struggled to explain why Trump counsellor Kellyanne Conway had declared the president retained "full confidence" in Flynn just hours before the adviser had to submit his letter of resignation.Flynn's firing heightened questions about the president's friendly posture toward Russia. Democrats called for investigations into Flynn's contacts and Republican Senator Lindsey Graham said Congress needed to know whether he had been acting with direction from the president or others.