WASHINGTON--Three federal agencies approved long-delayed U.S. mortgage market standards Tuesday, completing a less onerous rule than regulators originally proposed in the wake of the 2008 financial crisis.

The Federal Deposit Insurance Corp., Office of the Comptroller of the Currency and Federal Housing Finance Agency dropped a requirement that borrowers make a 20% down payment to get a so-called "qualified residential mortgage" amid concerns such an approach would hamper the ability of consumers to get home loans. Instead, banks will simply have to document a borrower's ability to repay their loans and ensure they only have a certain level of debt compared with their income.

The long-expected regulation wraps up a key unfinished piece of the 2010 Dodd-Frank financial overhaul law but is far from the rule regulators initially set out to enact. In the wake of the crisis, regulators wanted to ensure banks were only making loans that could be repaid. They proposed that banks either have "skin in the game" and hold 5% of the risk from the mortgages they packaged into securities and sold to investors--or require that borrowers make a 20% down payment to get a loan.

But housing industry trade groups and consumer advocates opposed the original proposal, arguing it would harm the fragile housing market and prevent many creditworthy borrowers from getting loans. So banking regulators backed down and issued a new proposal last year dropping the down-payment requirement and replacing it with a separate set of standards aimed at ensuring borrowers can repay their loans.

Officials said they were sensitive to mortgage industry concerns about the health of the U.S. housing market, and didn't want to add an extra layer of complexity that could constrain lending.

Martin Gruenberg, the FDIC's chairman, said the rule "promotes compliance" and minimizes costs for lenders by providing a unified federal standard for mortgage lending.

The FDIC's board voted 4-1 to approve the proposal. Jeremiah Norton, an FDIC board member, raised questions about whether the regulators have the authority to delegate their rule-writing responsibilities to the Consumer Financial Protection Bureau, saying that Congress specifically intended for the two rules to be separate.

The rule's passage "means more clarity for lenders and encourages safe and sound lending to creditworthy borrowers," said Mel Watt, director of the Federal Housing Finance Agency, in a prepared statement. "Lenders have wanted and needed to know what the new rules of the road are and this rule defines them."

The Federal Reserve, Securities and Exchange Commission and Department of Housing and Urban Development were expected to join the other regulators and approve the rule Wednesday. The rule, which goes into effect in fall 2015, will be reviewed for its impact on the economy four years later, and every five years after that.

Write to Alan Zibel at alan.zibel@wsj.com

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