Some officials believe the offering could raise around $30 billion and value the combined firms at roughly $500 billion or more.

U.S. President Donald Trump's administration could kick off initial public offerings of Fannie Mae and Freddie Mac later this year, according to a senior administration official, marking a key milestone for the mortgage finance giants that have been under government control for years.

More than a decade after the government bailed out the mortgage giants, the Trump administration is looking for a partial stock-market exit.