The Trump administration has attempted to kick-start the privatisation of Fannie Mae and Freddie Mac.
President Trump has said they would need to raise around $200bn to return to private control.
The US mortgage giants were bailed out by the taxpayer in 2008.
The new minimum capital proposals would require Fannie and Freddie to hold a combined $240bn — more than envisaged under an earlier plan in 2018 that did not come to fruition.
