Bloomberg reported that according to Ditlev Engel, chief executive officer of Vestas Wind Systems A/S, the biggest maker of wind turbines, that U.S. wind turbine sales may “fall off a cliff” unless lawmakers extend tax credits supporting the market beyond 2012.

Engel added “Our concern is that if the PTC is not extended, history has shown us that these markets tend to fall off a cliff,” and “We should prepare ourselves for it.”

Ending the PTC program would be a blow to producers including Vestas and General Electric Co., the third-biggest wind turbine maker, which are already struggling with falling prices amid increased competition from Chinese rivals.

According to the report, The American Wind Energy Association is lobbying congress to extend the tax measure. Until that’s done, the market for 2013 “has a question mark over it,” AWEA Chief Economist Elizabeth Salerno said on Oct. 25.