The U.S. Treasury on Friday said that it was taking steps to wind down Fannie Mae and Freddie Mac, the country's largest mortgage financiers that were taken over by the government during the financial crisis.

The government-controlled companies, which buy mortgages from lenders and repackage them as securities for investors, will be required to reduce their investment portfolios at an annual rate of 15% instead of the 10% required under their previous agreements with the Treasury.