Grief and determination has united Wall Street in an extraordinary way.

One week after the terrorist attack that crippled the world's major financial market, arch rivals are sharing facilities and thousands of traumatised employees have returned to work as part of the supreme effort to restore some semblance of normality.

At the New York Stock Exchange grief counsellors position themselves around the trading floor ready to provide support if necessary as traders suppress their emotions to focus on executing deals under strained conditions.

Displaying typical Wall Street toughness when asked if he had sought any psychological help, New York Stock Exchange chairman Mr Richard Grasso replied sharply that he didn't need it. "My counselling is this: that Monday morning 9.30 bell."

Electronic stock quote screens all carry the words "God Bless America".

It is both physically and emotionally difficult to get back to work in lower Manhattan. The hum of generators - providing emergency electricity supplies - drowns out all other noise in the area around Wall Street. On some streets generators outnumber people.

Workers in offices close to the World Trade Centre site are wearing surgical and gas masks as they go about their daily business as the stench of burning materials remains strong.

Firms based at the World Trade Centre are struggling to restore normal services to their clients. Agencies are providing temporary staff to help to ease the burden this week. Others have been forced to relocate.

About four million square feet of office space has been taken up in the past couple of days. The Real Estate Board of New York issued a warning on Friday calling on commercial landlords to make deals at the market conditions prevailing directly before Tuesday's attack.

Brokers have also been urged to waive their usual commissions when helping tenants to find temporary accommodation. "No one should benefit financially from this crisis," it warned.

Willaimson Picket Gross, which manages a large building on 116 John Street, supplied masks and food to tenants who arrived. Electricity at that site is being supplied by an outside generator but there will be no phone service for another two weeks.

AON, the insurance broker that occupied the 92nd to 105th floors at the World Trade Centre and is missing nearly 200 if its 1,350 employees in New York expects to open new offices today. Some staff have been working from home but have reported a deep sense of isolation.

Ms Melody Jones, AON's chief human resources officer, said she hopes people will find it therapeutic to be able to work together again in an office. "People would like to begin to do their work. It can be helpful in having something to focus on."

Merrill Lynch has been locked out of its headquarters across the road from the World Trade Centre. Staff are expected to remain on the other side of the Hudson river for the next couple of months.

On Monday the firm had to get by with only 60 per cent of its traders.

Goldman Sachs has full use of its main offices where the chairman, Mr Henry Paulson, spends much of the mornings on trading desks encouraging people to buy and sell stocks and bonds as always.

But the presence of sniffer dogs in the lobby to check incoming packages reflects changed times.