Natalie Konkel stood outside the Citigroup Center here Monday morning, nervously puffing a cigarette, hands shaking, trying to figure out what to do.

She had not followed news reports over the weekend. So she was shocked to emerge from the subway to find her office building surrounded by black-clad police officers in helmets and dark sunglasses, assault rifles gripped tightly across their chests.

Konkel, a 27-year-old marketing manager for law firm Kirkland & Ellis LLP, navigated security and made it to her office, where a voice mail message awaited.

The message, sent to all Kirkland employees, described the government warning issued Sunday afternoon saying al Qaeda terrorists had plotted to blow up the Citigroup tower in midtown Manhattan, as well as the New York Stock Exchange and the Prudential Financial Center in Newark, probably with car or truck bombs. Or perhaps the terrorists would poison the air in the buildings with biological or chemical weapons.

Konkel said the message advised Kirkland employees to decide for themselves whether to remain at work or take a bit of time off. It was not the way she expected to start the week -- with a virtual target on her back.

So Konkel decided to go home, steady her nerves and decide how to proceed, knowing the threat would still be there Tuesday. "I love my job," she said before leaving, "but I love my life more. . . . Right now, I just need to go home and pet my dog."

Konkel's reaction to the chillingly specific terror threats was certainly not universal among employees at the announced targets in New York and New Jersey.

At the stock exchange, many traders and executives brushed off the news and happily plunged back into the business of making money.

They have always been a target, several workers arriving at the exchange said. The only thing different Monday was more armed guards at barricades that have been around since the Sept. 11, 2001, terror attacks on New York and the District.

"I feel great. It's just like any other day. I'm not scared at all," said Mike Patton, who works on the floor of the exchange. Patton breezed through a security line and shook hands with NYSE chief executive John A. Thain and New York Sen. Charles E. Schumer (D), both of whom stood outside greeting arriving workers and assuring reporters that the threats would not deter vital functions of the U.S. economy.

"We have to make sure we are open for business as usual," Thain said. "People are happy to be here. They know this is their job. . . . I would say there is very little nervousness."

The business-as-usual response drew praise from Treasury Secretary John W. Snow. "Our nation's financial markets, financial institutions and financial sector continue to operate normally," he said in a statement Monday. "I applaud the financial services industry for remaining open for business."

On the exchange floor, after New York Mayor Michael R. Bloomberg (R) rang the opening bell, broker Robert H. McCooey Jr., president of Griswold Co., said the threat had raised the anxiety level, at least momentarily.

"Most people realize that coming to work here, they are always a target," he said. "But suddenly everyone focused on it again." But McCooey said fears faded once the bell rang and trading adrenaline kicked in. "Once people get in here, they get back into the daily routine."

Meanwhile, across the Hudson River in Newark, employees at the Prudential Financial office tower arrived to find fresh barricades, heavily armed police officers and blocked-off streets.

Throughout the day, Prudential security officials held "town hall meetings" with employees to discuss the terror threat and what was being done to protect workers. New Jersey Gov. James E. McGreevey (D) was to meet with Prudential Financial Inc. chief executive Arthur F. Ryan in the afternoon.

On the streets outside the Prudential building, employees mainly avoided the handful of reporters who descended on anyone who emerged.

But Stacey Parron, a business analyst for the giant insurance and financial services company, stopped. She said she was angry -- not at the company for asking her to treat the day as "business as usual," but at the terrorists for forcing people to live in fear.

"I came home last night, and I had lots of voice mails from family and friends," Parron said. Most of them told her to stay home. "I told them, 'Yes, it's my building that was threatened, and yes, I'm going to work.' My mother cursed my stubborn streak."

Back at the Citigroup Center, Abe Neidoff, an 81-year-old operating the register at the Market Card Shop in the complex's sunken courtyard, said he was much less afraid of terrorists than he was of losing business. Police had removed tables in the courtyard and made it harder for workers to come in and out.

"I think this is probably the safest place to be in New York today. I am not nervous at all," he said. "But I'm not getting any business. And I don't expect this to be a one-day affair."

A group of clearly disgruntled workers outside the Citigroup building, meanwhile, saw the threat level differently from Neidoff.

They spoke on condition of anonymity for fear of upsetting their employer. They said they wanted to work from home for at least a couple of days but, as of midmorning, had not been given the option. And they had little use for the happy warriors waltzing in the building with snappy sound bites for the television cameras.

"No one wants to be here," one member of the group said. "All the people saying they are so happy to be going to work, they are just lying."

A police officer stands outside the New York Stock Exchange. Inside, many had a "business as usual" response to the terrorism warnings.