Sanders will release a short statement on that day and then hold a major campaign kickoff in Vermont in several weeks, according to Vermont Public Radio.
A Democratic source close to the senator confirmed to The Hill that Sanders will announce his candidacy for the Democratic presidential nomination in a statement later this week, before heading back to his home state for a campaign kick-off event early next month.
Sanders' entry into the Democratic race ensures that Hillary Clinton will face a challenge to win the support of the liberal wing of the party.
Sanders' basic message will be that the middle class in America has been decimated in the past two decades while wealthy people and corporations have flourished.
SCROLL TO CONTINUE WITH CONTENT
Never Miss a Beat.
Get our best delivered to your inbox.
Just before 4:30 PM EST, Sanders sent this message out on his Twitter account:
This is government of the few, by the few and for the few. pic.twitter.com/5fuCwP1VRo
— Bernie Sanders (@SenSanders) April 28, 2015
Follow emerging reactions on Twitter: