The White House says U.S. President Barack Obama would veto the Republican “Plan B” tax proposal that is designed to avert the “fiscal cliff,” saying the plan places too large a burden on the middle class without balancing spending cuts and tax increases.

White House communications director Dan Pfeiffer says the Republican plan does not raise enough revenue from the country's top earners, would leave a substantial deficit-reduction burden on the middle class.

He said the proposed legislation, sponsored by U.S. House of Representatives Speaker John Boehner, would mean the wealthiest Americans would still benefit, while students and families would lose critical tax cuts, and health and unemployment benefits they need.

The House could vote Thursday on the bill that would extend low tax rates, except on income of $1 million and above.

Pfeiffer said the president is urging Republican leaders to work with the White House to find a reasonable solution. Without an agreement, a series of tax hikes and spending cuts will go into effect starting January 1.

He said in the unlikely event the bill were to pass the Senate, Mr. Obama would veto it.

Mr. Obama also has reduced his demand for more taxes over the next decade from $1.4 trillion to $1.2 trillion and said he would agree to a Republican call to curb spending for government pensions for retired workers by changing the way annual increases in the payments are calculated.

Even as they move closer to an agreement, the problem for Mr. Obama and Boehner is whether they can convince their political colleagues to support the emerging compromise. In the United States, Democrats have adamantly opposed any changes in Social Security, the pension plan for retirees, while Republicans have steadfastly stood against tax increases.

The two sides are trying to avoid what Washington is calling a “fiscal cliff,” about $500 billion in mandated spending cuts for defense and domestic programs and higher taxes throughout the U.S. labor force that are set to take effect January 1.