The U.S. Federal Reserve more than doubled its buying of mortgage bonds guaranteed by Fannie Mae (FNM), Freddie Mac (FRE) and Ginnie Mae in the second week of its program to support the housing market.

The central bank bought $23.4 billion in the week ended Jan. 14, after purchasing $10.213 billion in the previous week, it reported Thursday.

It has pledged to buy $500 billion, or more, of these bonds in the first half of the year, with the goal of pushing down mortgage rates.

The bulk of the Fed's purchases was of mortgage bonds guaranteed by Freddie. It bought $15.83 billion of its bonds, after buying $6.899 billion last week.

The bank bought $5.63 billion of Fannie bonds, following a purchase of $2.864 billion in the previous week.

It also bought $1.95 billion of Ginnie bonds. Last week, that figure was $450 million.

The Fed's program is one of many it is juggling as it expands its role in the financial markets.

Like last week, much of its buying was concentrated in the 30-year 4%, 4.5% and 5% coupons, according to Fed data.

The current coupon or that closest to par is the mortgage bond with a primary mortgage rate of 4% on its 30-year loans. Typically, lenders add additional charges and fees to this primary rate to come up with the final mortgage rate homeowners pay.

-By Anusha Shrivastava, Dow Jones Newswires; 201-938-2371; anusha.shrivastava@dowjones.com

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