National security adviser General Michael Flynn delivers a statement daily briefing at the White House in Washington U.S., February 1, 2017. REUTERS/Carlos Barria

Former Trump national security adviser Michael Flynn will plead guilty to one count of making false statements to the FBI. In the latest sign that the special counsel’s investigation is intensifying, special counsel Robert Mueller has charged Flynn with “willfully and knowingly” making “false, fictitious and fraudulent statements” to the FBI regarding conversations with Russia’s ambassador Sergey Kislyak.

He’ll appear at a federal courthouse in Washington before U.S. District Judge Rudolph Contreras for a plea hearing Friday morning.

Flynn is the first Trump administration official – and the fourth connected to the campaign – to be charged as part of Mueller’s investigation into possible collusion between the Russian government and members of Trump’s team, as well as potential obstruction of justice and financial crimes.