FACTBOX: U.S. House mortgage assistance plan

WASHINGTON (Reuters) - The U.S. House of Representatives on Thursday approved legislation that would let the government backstop as much as $300 billion worth of troubled mortgages and offer billions more to stabilize the country's housing market.

Senate Democrats have promised action on similar legislation and the House vote puts the ball in their court.

Below are some of the key provisions of the House bill, which faces the threat of a veto from the White House:

-- The Federal Housing Administration, the largest U.S. homebuyer aid program, would receive a new mandate and cash infusion to guarantee mortgages where the home has decreased in value since the original loan was written. Mortgage investors could receive an FHA guarantee on loans after erasing a large share of the original loan amount. Although the government would be authorized to backstop $300 billion in loans, the program would likely only affect an estimated $85 billion worth, according to the non-partisan Congressional Budget Office. CBO said the program could aid 500,000 borrowers at a cost of $2.7 billion.

-- Local governments would receive $15 billion in federal grants to buy and restore foreclosed homes that have fallen into disrepair.

-- First-time homebuyers would receive a $7,500 tax credit to be repaid, interest free, over fifteen years.

-- States would be authorized to issue $10 billion of fresh tax-exempt bonds to buy home loans headed toward foreclosure.

-- The legislation would expand a federal guarantee of home loans to veterans and give them additional protection from foreclosure.

-- The legislation includes two housing reform measures that have previously cleared the House: a provision to modernize the current FHA program by loosening some underwriting standards and a measure to create a new regulator for Fannie Mae and Freddie Mac, two government-chartered mortgage finance companies.

(Compiled by Patrick Rucker)