NEW YORK (CNN/Money) - Investors will be keeping one eye on holiday sales and the other on reports of possible terror attacks against the United States as Wall Street heads back to work Monday.

S&P and Nasdaq futures edged lower in before-hours trading, pointing to a weak to mixed start for stocks.

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Stocks ended mixed Friday with blue chips posting gains for the week. This week will bring a holiday-shortened trading schedule, which could make investors hesitant to make big moves. (For more on last week's trading, click here).

The Bush administration Sunday raised the national terror threat level to "high" from "elevated," with Homeland Security Secretary Tom Ridge warning of possible terrorist strikes more devastating than those of Sept. 11. The warnings could chill holiday travel -- and perhaps holiday shopping with just three days left until Christmas.

The increase in the alert level drove stock futures lower Sunday night but the contracts had bounced back by Monday morning.

Overseas, stocks rose inAsia, where investors shrugged off the heightened terror alert in the United States. Stocks were mixed in Europe.

Treasury bond prices rose, pushing the yield on the 10-year note to 4.11 percent from 4.13 percent late Friday. Bond prices and yields move in opposite directions.

The dollar hit another record low against the euro and also fell against the Japanese yen.

On Wall Street, a shortened trading schedule could make for lighter-than-normal volume, which could make things choppy. (For a list of the week's key events, click here..)

"Everybody is done with the year now, so it's just going to be traders that dominate the tape," said Tony Dwyer, equity market strategist at FTN Midwest Research. "I think that you're going to see a lot of intraday volatility without much real movement."

But some investors and analysts still think the market, after its already strong gains this year, could move higher still

No major economic reports are scheduled for Monday.

U.S. financial markets will be closed Thursday for Christmas. The stock market will close at 1 p.m. ET, Wednesday and Friday. Bond, commodity, and currency markets will close around noon ET Wednesday and Friday, while oil trading on the New York Mercantile Exchange is set to end at 1 p.m. ET.