Morgan Stanley, the second-biggest U.S. securities firm, plans to cut 600 jobs after a decline in mortgage-related revenue led to lower third-quarter earnings than analysts estimated.

About 500 jobs will be eliminated in the United States and about 100 in Europe, including 90 from a U.K. mortgage subsidiary, the New York-based firm said today in a statement. The cuts represent about 25 percent of Morgan Stanley's residential mortgage origination and servicing jobs, said spokesman Mark Lake. They are just over 1 percent of the firm's entire work force.