The cuts are believed to be in addition to the 2,200 people Interpublic said it cut in the first half of this year.
Advertising and media revenue decreased 8% to $1bn (£700m) from last time, reflecting reduced client spending, particularly on media.
Second-quarter revenue decreased 4.3% to $1.7bn(£1.2bn). Net income before one-time costs was $117m (£82m) in this year's second quarter, compared with $201.4m (£141m) last time. The inclusion of True North, the $1.7bn (£1.2bn) acquisition completed in June, added modestly as expected.
Interpublic said that it would take a charge of $500m (£350.5m) in restructuring during 2001. These charges relate to the recently announced company reorganisation and the integration of True North.
The costs also include the thousands of job cuts announced, many of which will come from the integration of backend services following the reorganisation and the integration of True North.
The company said that the cost-cutting initiatives exceed earlier estimates due to the worsening economic climate.
John Dooner, chairman and CEO, said Interpublic, as a company, did not reduce costs as quickly and as deeply as needed.
"While our recent reorganisation improves the quality of our client offering and provides the operational foundation for accelerated long-term organic growth, we also recognise the need for aggressive and immediate action to provide a strong financial foundation from which to deliver that growth," he said.
Sean Orr, Interpublic chief financial officer, said, "The need for these aggressive cost cuts intensified when the rate of client spending decelerated more swiftly than anticipated in May and June, and resulted in changes to our revenue forecast."
Domestic revenue declined 7.3% to $986.8m (£692m) while international revenue was flat at $756.6m (£530.5m). In constant dollars, international revenue was 8% higher, reflecting stronger top-line performances in Europe and Latin America.
Net new-business wins totalled $846m (£593.2m) during the second quarter. With this growth, Interpublic's brands increased their market share of advertising and marketing services industry revenue.
Major new account wins during the quarter included Exxon-Mobil won by McCann-Erickson, General Mills won by Campbell-Mithun and Verizon won by Lowe Lintas.
Interpublic is now comprised of four global operating groups, which are McCann-Erickson WorldGroup, The Partnership, FCB Group and Advanced Marketing Services. Major global brands include: Draft Worldwide; Foote, Cone & Belding Worldwide; Golin/Harris International; Initiative Media; Lowe Lintas & Partners; McCann-Erickson; Octagon; Universal Media; and Weber Shandwick.