WASHINGTON — The Federal Housing Finance Agency is extending its Home Affordable Refinance Program for another year, the agency said Thursday.

Fannie Mae and Freddie Mac have already refinanced 3.4 million homeowners through the program. But the government-sponsored enterprises' regulator says another 143,000 GSE borrowers with high loan-to-value loans could still benefit from a refinancing through the program.

"To ensure that high LTV borrowers who are eligible for HARP continue to have a refinance option, FHFA is also directing the enterprises to extend HARP through December 31, 2018," the agency said.

The agency also announced that the GSEs are making modifications to streamline their refinancing programs for existing Fannie and Freddie borrowers whose loan-to-value ratios exceed the maximum allowed for a standard refinancing.

These new refinancing options will go into effect once the refinance program expires on Dec. 31, 2018.

Under the streamlined program, the date on the mortgages being refinanced must be on or after Oct. 1, 2017, according to the guidelines issued by Fannie and Freddie.