UPDATE 3-White House threatens to veto energy bill

(Recasts, updates with analyst comments)

By Chris Baltimore

WASHINGTON, Dec 3 (Reuters) - The White House on Monday threatened to veto legislation pending in the U.S. House of Representatives that would require the first big increase in three decades in the country's automobile fuel efficiency.

Congressional Democrats have hammered out a complicated deal that could result in a 40 percent boost in fuel efficiency standards by 2020.

The White House said it opposed provisions expected to be included in the bill that would require utilities to get 15 percent of their electricity from renewable sources by 2020, and raise taxes on oil and natural gas companies.

"It appears Congress may intend to produce a bill the President cannot sign," top White House economic advisor Allan Hubbard said in a letter to House Speaker Nancy Pelosi.

The keystone of the House energy bill -- expected to see a vote this week -- would raise fuel-economy standards to 35 miles per gallon (6.72 liters per 100 km).

The White House has backed a rise in fuel economy standards as well as a boost in renewable fuels like ethanol, which is also expected to be included.

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