NEW YORK (Reuters) - Stocks slid on Monday as a brokerage downgrade of Citigroup Inc  sparked a sell-off in financial services companies on concerns about credit losses and the housing slump.

Citigroup, Inc (NYSE)



Goldman Sachs cut Citigroup to "sell" and said the bank may have to write off $15 billion over the next two quarters as mortgage losses reduce earnings.

Investors also got hit by more disappointing news on the housing front. Lowe's Cos. Inc, the No. 2 U.S. home improvement chain, slashed its full-year profit outlook, underscoring the toll on consumers of the drop in home values.

In addition, a brokerage said Freddie Mac, the No. 2 U.S. home funding source, may suffer between $1 billion and $5 billion of subprime mortgage losses.

"Financials keep on going down," said Giri Cherukuri, head trader at OakBrook Investments LLC, which oversees $1.3 billion in Lisle, Illinois. "You had the Citigroup downgrade and there are general worries about how many more writeoffs there are to come."

The Dow Jones industrial average <.DJI> was down 150.96 points, or 1.15 percent, at 13,025.83. The Standard & Poor's 500 Index <.SPX> was down 19.41 points, or 1.33 percent, at 1,439.33. The Nasdaq Composite Index <.IXIC> was down 32.93 points, or 1.25 percent, at 2,604.31. View more of todays Stock Market Summary.

In the bond market, prices rose and yields dropped to two-year lows as investors bought Treasuries in a safe-haven move away from stocks. The benchmark 10-year note rose 11/32 for a yield of 4.13 percent.

Citigroup shares fell 5.2 percent to $32.26 on the New York Stock Exchange, while shares of Bank of America Corp (BAC.N: Quote, Profile , Research), the No. 2 U.S. bank, declined 3.3 percent to $42.89.

Shares of JPMorgan Chase & Co, the No. 3 U.S. bank, shed 3.4 percent to $42.63. The S&P financial index slid 3.03 percent.

Shares of Lowe's slumped more than 6 percent to $23.38 after the retailer slashed its full-year profit outlook. Shares of top-ranked rival Home Depot Inc (HD.N: Quote, Profile , Research) declined 2.1 percent to $28.47. The S&P retail index <.RLX> was down 2.5 percent.

Shares of Freddie Mac declined 8.9 percent to $37.10 on the NYSE after Credit Suisse said in a research note the company may recognize a loss of between $1 billion to $5 billion on its subprime AAA portfolio.

The KBW mortgage finance index tumbled 5.2 percent.

On the Nasdaq, shares of Apple Inc (AAPL), the iPhone maker, led decliners, falling nearly 1 percent to $164.62. The stock, along with other sector bellwethers such as Research In Motion Ltd (RIMM), have been on the defensive on concern that the credit crisis may hurt technology spending.

(Additional reporting by Kristina Cooke; Editing by Kenneth Barry)