Fannie Mae and Freddie Mac, the largest US mortgage-finance companies, won’t be able to repay all of the $84.9 billion in federal aid they have received since being seized by the government last year, their regulator said.

“Some assets and senior preferreds will have to be left behind as they come out of conservatorship, and that means some of those losses will never be repaid,” Federal Housing Finance Agency Director James Lockhart said in a speech in Washington yesterday.

“Their book is so large, it’s hard for me to see that they will be able to repay.”