He said that if the US market continued to dip, Havas might not meet this year's target of 10%-15% average growth over the next two years.
He said, "If the United States goes down in the second quarter it would not be reasonable to maintain 10% organic growth."
However, de Pouzilhac was upbeat about the outlook for 2001 and went on to say that it was "very likely that in the first half we will do significantly better than in 2000".
Havas shares were up 7.5 % points on the day last night to €16.02 (£9.71), having hit €16.50 (£10) in the afternoon.
Earlier this week in the US, Havas-owned agency Arnold Worldwide was named agency of record by the Washington Post.
Havas was hit hard by the disappearance of dotcom ad budgets in the first quarter of 2001 and saw new business fall 15% compared with the same period last time. However, excluding dotcoms new business rose 4.5% to €883m (£537.2m).