WPP is expected to cut its full-year sales forecast when it releases its latest financial figures tomorrow.
If it does, it will be the second cut in its forecast in the past six months.
Analysts expect the marketing services company to report that sales for the first half of the year fell 7.9% to £4.27 billion.
On the release of figures in April, WPP said that although the second half of 2009 would continue to be tough, it was likely to improve relatively, with any recovery probably coming in 2010.
The company reported a 5.8% year on year fall in like-for-like revenue for the first three months of the year.
Its UK operations increased revenue by 16% year on year in the first quarter, totalling £251.1 million.