Nancy Pelosi, John Boehner, Barack Obama and Harry Reid

President Barack Obama's offer to slow the growth of Social Security benefits would force fellow Democrats in Congress to abandon promises to shield the massive retirement and disability program from cuts as part of negotiations to avoid the year-end fiscal cliff.

Both Senate Majority Leader Harry Reid, D-Nev., and House Minority Leader Nancy Pelosi, D-Calif., pledged not to touch Social Security as part of deficit reduction talks.