WASHINGTON (Reuters) - U.S. President Barack Obama will call in his State of the Union address on Wednesday for an extension of a tax break to businesses that allows them to

write off investments in equipment more quickly.

The tax break, a 50 percent "bonus depreciation" through 2010, is worth $38 billion over the 2010-2011 period, a senior administration official said.

"It will allow businesses to recover the costs of capital expenditures faster than ordinary depreciation schedules by permitting these businesses to immediately write-off 50 percent of the cost of depreciable property, for example equipment, tractors, wind turbines, solar panels, and computers," the official said.

"To put the magnitude in perspective, this tax cut represents about 13 percent of all expected corporate tax receipts in 2010."

(Editing by Cynthia Osterman)