WASHINGTON – House Speaker John Boehner said Wednesday that "serious differences" remain between him and President Barack Obama in negotiations on averting automatic spending cuts and tax increases that economists fear could send the U.S. economy over a "fiscal cliff."

Boehner's comments came as top Democrats pushed back on GOP demands for tough steps like raising the Medicare eligibility age and curbing the cost-of-living adjustment for Social Security.

Boehner and Obama spoke on the phone twice Tuesday, a day after the president offered to reduce his initial demand for $1.6 trillion in higher tax revenue over a decade to $1.4 trillion. But Obama continued to insist that much of the revenue come from raising top tax rates on the wealthy.