US President George Bush says mortgage giants Freddie Mac and Fannie Mae have been taken over because they posed "an unacceptable risk" to the economy. The two companies account for nearly half of the outstanding mortgages in the US, and have lost billions of dollars during the US housing crash. The most recent figures show about 9% of US mortgage holders were behind on their payments or faced repossession. The federal takeover is one of the largest bail-outs in US history. It was announced on Sunday by Treasury Secretary Henry Paulson. "Putting these companies on sound financial footing, and reforming their business practices, is critical to the health of our financial system," President Bush said.