(FILES): This December 21, 2016 file photo shows US President-elect Donald Trump (L) with with Trump National Security Adviser designate Lt. General Michael Flynn (R) at Mar-a-Lago in Palm Beach, Florida.
The White House announced February 13, 2017 that Michael Flynn has resigned as President Donald Trump's national security advisor, amid escalating controversy over his contacts with Moscow. In his formal resignation letter, Flynn acknowledged that in the period leading up to Trump's inauguration: 'I inadvertently briefed the vice president-elect and others with incomplete information regarding my phone calls with the Russian ambassador.'
Trump has named retired lieutenant general Joseph Kellogg, who was serving as a director on the Joint Chiefs of Staff, as acting national security advisor, the White House said. / AFP / JIM WATSON / XGTY (Photo credit should read JIM WATSON/AFP/Getty Images)