With less than a month to go before her organisation's annual fundraising gala, which is due on November 3, and just over half the tickets sold, Jane Aronson is diligently working the phones.

"I'm going into my database to see who's come in the past and I'm calling," said the paediatrician and founder of Worldwide Orphans Foundation, a New York-based non-profit organisation.

Dr Aronson said the foundation had commitments for $900,000 (€664,285. £525,510) in tickets, but not everyone had paid. Individual tickets start at $1,000 and tables go for $10,000-$100,000. Last year's gala, which was sold out, raised $1.4m.

"We've always sold tables to Bear Stearns, Lehman, Merrill Lynch, you name the company, and they bought a table and filled it with 10 or 12 people," she said. "We have so many companies that aren't buying tables and then people who aren't buying tables because their business was affected by [the financial crisis]."

As the credit crisis deepens, US charities are bracing for a decline in giving from both corporations and financially stretched individuals. According to the Giving USA Foundation, a group that looks at trends in philanthropy, charitable giving fell during past downturns.

In slumps, in 1973 and again in 2001, donations failed to keep pace with the growth in inflation for three years straight. Giving declined in 1987 - when the stock market fell more than 18 per cent over the course of a few days. In the worst recession year for giving, 1974, contributions fell by a total of 5.4 per cent. The following year, giving fell 2.7 per cent.

Del Martin, chairman of the foundation, projects that giving this year will be "flat, or we'll see a slight dip from last year" when individuals and institutions made $306.69bn in charitable donations and pledges.

It is unclear how severely this economic decline will affect the non-profit world, but development officers at charities are particularly nervous about the prospect of raising money in a prolonged economic recession.

Giving by individuals, dropped an average of 4 per cent in the four years with eight months or more of recession. Foundation giving, which makes up about 10 per cent of the total, fell an average of 0.1 per cent in those years, and corporate giving, which accounts for about 5 per cent of total giving, fell an average of 1.6 per cent in those years.

Clara Miller, president of the Nonprofit Finance Fund, which helps finance non-profits and consults on their financial matters, said charities were worried. "From a philanthropy point of view, there is a collective holding of the breath, and asking: 'How bad is this going to be?','" she said. "New givers are likely to retreat, while longtime givers are likely to stand stalwart."

Howard and Janet Kagan, longtime donors who are on the board of several charities - Mr Kagan on Planned Parenthood of New York City and Ms Kagan on Children's Rights Watch a division of Human Rights Watch, say they remain "very committed" and "don't have any plans to pare back".

"People need to keep things in perspective; there are going to be times like this from time to time ," said Mr Kagan. "This is when non-profits do their best work; this is when the need grows."