A source is confirming that Newton Mayor Setti Warren plans to drop his bid for the US Senate seat in 2012. The Boston Globe first reported the development.

The source said Mayor Warren told a core group of supporters at a meeting in Back Bay that he would be pulling out of the race for the Democratic nomination. His decision comes weeks after Harvard professor Elizabeth Warren jumped in the race to face off against US Sen. Scott Brown, a Wrentham Republican. Five other Democrats are also running.

Mayor Warren is expected to deliver a "formal address on the future of his campaign" outside of his family home in Newton on Beaumont Ave., according to the campaign.