NEW YORK (CNN/Money) - U.S. stock futures fell Monday as investors worried about a possible terrorist threat to the nation's financial institutions, including the New York Stock Exchange.

Early Monday, Nasdaq and S&P futures pointed to a lower start for the major indexes.

Among U.S. stocks trading in Europe, Citigroup (C: Research, Estimates) declined nearly 2 percent. The financial services company's New York headquarters is one of the potential al Qaeda targets named Sunday by Homeland Security Secretary Tom Ridge; security has been stepped up at the midtown Manhattan skyscraper.

Other potential targets named by Ridge include the NYSE in lower Manhattan, the headquarters of Prudential Financial (PRU: Research, Estimates) in Newark, N.J., and the World Bank and International Monetary Fund in Washington.

The major indexes are coming off a successful week, capped by Friday's 10-1/2 point gain for the Dow Jones industrial average and 6-1/3 point advance for the Nasdaq composite index (see chart for details)

For details of Friday's advance, click above.

Asian-Pacific stocks reacted to the increased terror concerns with declines Monday; Tokyo's Nikkei index fell 0.9 percent. European markets retreated in morning activity. (Check the latest on world markets)

In a flight to safety by investors, Treasury prices rose, sending the 10-year note yield down to 4.45 percent from 4.47 percent late Friday. The dollar pulled back against the yen and euro. Gold was higher.

Oil prices eased after being higher early. U.S. crude futures hit a record high of $43.92 a barrel in electronic trading, but then fell to $43.65, off 14 cents from previous levels. Brent oil futures slipped 14 cents to $39.89 a barrel in London.

In other corporate news, shares of Apple Computer (AAPL: Research, Estimates) lost about 3 percent in European trading Monday, and shares of Pixar Animation Studio (PIXR: Research, Estimates) could also be hit after news over the weekend that Steve Jobs, the CEO of both companies, had successful surgery for a rare form of pancreatic cancer.

Cox Enterprises, the largest shareholder of Cox Communications (COX: Research, Estimates), made an offer Monday to buy the remaining shares to take the nation's No. 4 cable company private. Privately held Cox Enterprises, which already owns 62 percent of shares, is offering $32 a share in cash for Cox Communications, which represents a 16 percent premium over Friday's closing price.

Network computer maker Sun Microsystems (SUNW: Research, Estimates) is considering making acquisitions, according to a report in Monday's Wall Street Journal. Sun President Jonathan Schwartz told the paper it has looked at "a number of acquisitions," including software maker Novell (NOVL: Research, Estimates), although he said it has not held talks with Novell.

Economic reports due Monday include the latest reading on construction spending and the state of manufacturing.

The Institute of Supply Management's index measuring the state of manufacturing is due at 10 a.m. ET. Economists surveyed by Briefing.com forecast the ISM index will be up to 62 for July from 61.1 in June.

The Census Bureau report on June construction spending is also due at 10 a.m. ET. Economists forecast that spending will be unchanged after a gain of 0.3 percent in May.