(Bloomberg) — Radian Group Inc. and MGIC Investment Corp. are among mortgage insurers that would need to fill a financial gap under new financial-strength rules proposed by the Federal Housing Finance Agency. The stocks dropped in New York trading.

Radian said it would need about $850 million to meet the standard now and expects to be able to comply within a two-year transition period allowed under the rules. Milwaukee-based MGIC didn't provide a figure and said it faced a “material shortfall.” Genworth Financial Inc. said yesterday that it may need as much as $550 million at its mortgage insurer by June 30, 2015, to meet the standards.

U.S. regulators are seeking to stiffen standards for mortgage insurers that back loans sold to Fannie Mae and Freddie Mac to prevent a repeat of the losses the government-backed firms faced in the 2008 financial crisis. Radian and MGIC said the rules are too stringent and could make it more difficult for borrowers to afford homes.