UPDATE 1-RESEARCH ALERT-Cowen cuts Ariba to neutral

(Recasts; adds details; share movement)

Sept 29 (Reuters) - Cowen and Co downgraded Ariba Inc's (ARBA.O) stock to "neutral" from "outperform," saying Wall Street's estimates for the software company's bookings growth were aggressive.

Shares of the company were down about 13 percent at $13.18 in afternoon trading on Nasdaq.

In a note, analyst Peter Goldmacher said bookings momentum is peaking and that the fourth quarter was usually a seasonally weak quarter for the company. "FY09 bookings growth forecasts are actually ahead of FY08 bookings growth when we back out specific one-time growth catalysts from FY08," he said.

Goldmacher believes that the most likely customers expected to drive the company's growth are taking an increasingly conservative approach to deploying new technology, potentially limiting margin upside to 2009 estimates.

The brokerage also said the fourth quarter will be the last full quarter of growth boosted by the company's acquisition of privately held Procuri Inc, a provider of supply management software, in the first quarter of 2008. (Reporting by Shrutika Verma in Bangalore; Editing by Amitha Rajan)