The federal regulator of Fannie Mae and Freddie Mac plans to lower the mortgage fees paid by some borrowers, but the move would amount to only modest help for risky buyers with checkered credit histories.

The Federal Housing Finance Agency is expected to announce in coming days changes to fees that Fannie and Freddie charge lenders to guarantee mortgages, according to people briefed on the matter.

For those borrowers affected by the changes, the benefits would be tiny, amounting to less than one-tenth of a percentage point. Fannie and Freddie, which back most home loans, will raise fees for other borrowers, like those who buy investment properties, to balance out the cost of the fee reduction. The changes are not expected to have any effect on revenue.

Julia Gordon, senior director of housing and consumer finance for the Center for American Progress, said the change in fees was in the right direction but didn’t go far enough. “Hopefully over time we can go further,” she said.