The company said its revenue for 2011 would be €6.4 billion, a reduction of 3% on its previous forecast of €7 billion. The revenue fall is down to lower production volume and additional costs of around €35 million.
Vestas said it was postponing handing over a number of projects in Europe, in order to maintain quality levels.
Speaking about the warning, Vestas CEO Ditlev Engel said: "Even though we have previously emphasised the risks involved in the fact that a large proportion of revenue is generated in the latter part of the year, I deeply regret that we have been compelled to take this unsatisfactory decision.
"I want to stress that safety and quality has top priority in Vestas and a decision to speed up the projects in question would have been irresponsible. The projects will of course be completed during 2012, and it is important also to point out that earnings on the individual projects are still satisfactory."