Treasury Secretary Tim Geithner, expected to leave his post after four years, is likely to stay on through what promises to be a bitter battle over the "fiscal cliff" and until his successor is confirmed, according to people familiar with the situation.

Geithner is said to want to ensure a smooth transition at Treasury at a time when critical issues are to be decided, including negotiating with Congress over the so-called fiscal cliff, tax reform and implementation of the Dodd-Frank financial overhaul.