Updated at 4:30 p.m. ET
President Obama on Friday will announce that White House Chief of Staff Rahm Emanuel is resigning in order to run for mayor of Chicago.
White House spokesperson Robert Gibbs said today that there will be a "personnel" announcement in the East Room of the White House Friday morning. He would not confirm that the "personnel" announcement referred to Emanuel, but CBS News has confirmed Emanuel's departure.
Emanuel already has a campaign manager,, and is expected to return to Chicago immediately to begin collecting signatures to get his name on the ballot.
Mr. Obama is expected to name White House senior adviser Peter Rouse as an interim replacement for Emanuel, according to Ambinder. Gibbs said today "there's a completely loyalty and trust" between the president and Rouse. He noted that Rouse has worked for Mr. Obama since his days as a senator-elect.
Gibbs added that there was nothing unusual about White House senior staffers leaving halfway through the president's first term.
"It is the natural course of Washington," he said.
Emanuel, a former Illinois congressman, has expressed interest in running for mayor of Chicago and was said to be considering the move since current Mayor Richard M. Daley announced he would not seek re-election.
Stephanie Condon is a political reporter for CBSNews.com. You can read more of her posts here. Follow Hotsheet on Facebook and Twitter.