WASHINGTON, Aug 7 (Reuters) - Freddie Mac FMCC.OB , the government-owned mortgage finance company, on Wednesday said it is considering legal action against Richmond, California, if the city uses eminent domain to seize mortgages of local residents who owe more than their properties are worth in a bid to keep them in their homes. The northern California city recently sent notice to the holders of more than 620 so-called underwater home mortgages in the city, asking them to sell the loans to the city. It would buy the mortgages for 80 percent of the fair value of the homes, write them down and help the homeowners refinance their loans. "Our sense is that those so-called voluntarily loan sales would not be very voluntary," said Freddie Mac's general counsel William McDavid in a conference call with reporters to discuss the company's second-quarter financial results. "They're loan sales under pressure - in fact, under a threat of seizure by eminent domain. We would consider taking legal action." Freddie Mac and its larger sister company, Fannie Mae, are some of the biggest buyers of private home-loan bonds. The two government-backed companies' finances would be affected if the eminent domain plan went forward and wiped out the worth of those bond investments. "Fannie Mae and Freddie Mac are investors in these securities. This is an issue that we are discussing," said Denise Dunckel, a spokeswoman for the companies' regulator, the Federal Housing Finance Agency.