NEW YORK (CNN/Money) - Merrill Lynch said Tuesday that it will cut back its Nasdaq trading, limiting its activities to the 2,400 most widely held stocks.

Merrill, the biggest full-service brokerage house in the United States, said it previously made a market in the approximately 3,900 Nasdaq-listed stocks and about 6,100 over-the-counter stocks that don't meet Nasdaq listing requirements.

As part of the move, Merrill will consolidate trading at its New York headquarters, stop trading at its Jersey City, N.J., facility and operate as one broker-dealer. It did not say whether any job cuts will result.

"While we may reduce headcount at some areas, we're also selectively hiring in others, such as our foreign exchange, derivatives and mortgage businesses," Merrill spokeswoman Jessica Oppenheim said. "Based on our current assessment of the environment, we think the bulk of headcount cuts have already been made."

On Monday, Merrill, which employs more than 50,000 people and already has cut about 15,000 jobs in the past year, denied published reports that it planned to cut more jobs. On Friday, a source said J.P. Morgan Chase is cutting its investment banking staff by as much as 20 percent.

Shares of Merrill Lynch (MER: up $0.67 to $29.10, Research, Estimates) were little changed Tuesday afternoon.

Merrill said its new trading universe represents about 92 percent of the total year-to-date volume on the Nasdaq National Market System and includes all of the Nasdaq stocks in the major indexes, including all Nasdaq components of the Russell 3,000 index.

"This is really what our clients want -- focused service in the most widely held stocks," Oppenheim said.

Merrill's move also is likely a response to the rising cost of accessing the market, associated with the Nasdaq's new "SuperMontage" trading system and rival electronic communications networks, or ECNs, such as Instinet and Island.

It's also possible that Merrill is trying to recover from paying a premium for its July 2000 acquisition of Herzog Heine Geduld, which was formally integrated with Merrill's Nasdaq businesses earlier this year.