The number of U.S. households on the verge of losing their homes dipped in May from April, and the annual increase was the smallest in three years.

But as layoffs, rather than risky mortgages, become the main reason that borrowers default on their home loans, foreclosures likely will remain elevated this year and into 2010. Many economists expect unemployment, now at 9.4 percent nationwide, to rise as high as 10 percent, and some project it will exceed the post-World War II record of 10.8 percent.