Corning (GLW) - Get Report was down 3.2% in preopen Instinet trading after Merrill Lynch cut its intermediate-term rating on the stock to neutral from accumulate.

Merrill said Corning's high-margin fiber-optic cable business, which represents 20% to 25% of sales, will be "below our worst-case scenario" over the next few quarters. Merrill said it now expects the stock to produce a favorable return in 12 to 18 months, as opposed to a previous expectation of 12 months.

Merrill is maintaining its long-term buy rating.