The number of homes taken back by lenders in the first half of this year fell 30 percent compared with the same 2010 period, the result of delays in foreclosure processing that threaten to stall a U.S. housing recovery.

Banks seized 421,212 homes in the first six months of the year, down from 529,633 between January and June last year, foreclosure listing firm RealtyTrac Inc. said Thursday.

The decline reflects lenders taking longer to move against homeowners who have fallen behind on their mortgage payments. The banks are working through foreclosure documentation problems that first surfaced last fall and an ensuing logjam in some state courts. Lenders also have put off on taking action against delinquent borrowers as U.S. home sales have slowed this year.

As the processing delays mount, however, so has the backlog of potential foreclosures -- homes that otherwise would have been repossessed by lenders this year.

RealtyTrac estimates that 1 million foreclosure-related notices that should have been filed by banks this year will be pushed to next year. The filings include notices for defaults, scheduled home auctions and home repossessions -- warnings that can lead to a home eventually being lost to foreclosure.