Vestas Wind Systems A/S, the world's biggest wind-turbine maker, declined the most in more than two years in Copenhagen trading after Morgan Stanley reduced its recommendation on the stock.

Vestas fell as much as 57 kroner, or 9.7 percent, to 530 kroner, the steepest one-day drop since Aug. 24, 2006. The shares traded at 535 kroner as of 1:30 p.m. local time, valuing the Randers, Denmark-based company at 99.1 billion kroner ($19.4 billion).

Morgan Stanley cut its rating on Vestas to ``underweight'' from ``equal-weight'' yesterday, citing ``early signs of softening demand among small developers'' and the recent increase in raw material prices, particularly steel, which it said would constrain profit margins.