Some experts were skeptical of the plan announced Thursday to get the stock markets up and running, given the extensive physical - and psychological - damage caused by the terrorist attack that demolished the World Trade Center.

''It's going to be a long weekend, but they'll probably be limping along on Monday,'' said Dave Farber, a professor of telecommunications at the University of Pennsylvania.

The NYSE, the Nasdaq Stock Market and the American Stock Exchange planned extensive testing on Saturday to make sure systems work.

''The right thing to do for America and certainly for those who are in the midst of this great tragedy is to resume trading,'' NYSE chairman Richard Grasso said. ''We are very confident we will have the right number of people on campus here and in the community required to bring up the world's most admired markets.''

While the stock markets remained closed for the third straight day Thursday - the longest closing since the crash of 1929 - some trading of government bonds and commodities took place as both the Chicago Board of Trade and Chicago Mercantile Exchange reopened.

Prices for Treasury bonds and notes skyrocketed as investors sought out a safe haven following the terrorist attacks.

Although the NYSE, Nasdaq and Amex's trading abilities were not directly harmed by the attack and most big financial firms have backup offices where they can do business, extensive logistical problems still exist.

The NYSE's trading floor is in the financial district, meaning that the area has to be made safe enough for traders and others to get there.

Grasso estimated between 75,000 and 100,000 people would come in to work when the markets reopened. Travel in lower Manhattan is restricted because of fears that the buildings are unstable.

The Amex, which was closer to the World Trade Center, sustained enough damage that its trading floor is not usable. Its operations are expected to be temporarily relocated to the NYSE and other regional markets.

The Nasdaq's administrative headquarters are across from the World Trade Center, but most of its trading is done electronically.

But all three markets rely on telephone lines and other infrastructure in the financial district.

Girders plunged through the brick walls of the Verizon switching building that controls 40 percent of lower Manhattan's telephone lines and 20 percent of those used by the NYSE. The impact smashed computer equipment and left a half-inch layer of dust. Water also flooded the building's sub-basements, which are home to the cables used to connect Wall Street.

Many financial firms have simply moved their offices and their trading desks to temporary quarters outside Manhattan, mainly in New Jersey. But offices that perform functions necessary for trading and are still standing will have to make a decision.

Although Merrill Lynch's trading operations are outside the financial district, it still has offices in the area for legal and other support services.

''It's too early to say, but most likely, all those operations will be done out of other offices,'' said spokesman Eddie Reeves.

Those who return to Wall Street Monday must also deal with sadness and trauma. An estimated 4,700 people have been reported missing.

Securities and Exchange Commission chairman Harvey Pitt praised the decision to wait until Monday: ''This is a positive development and should give investors even more confidence.''