May 17 (Reuters) - Cisco Systems Inc (CSCO.O) said on Wednesday a large backlog of products due to supply chain constraints has hit demand for new orders from customers, sending the company's shares down 4% in extended trading. Cisco's product orders fell 23% in the third quarter, even as the maker of routers, security services and software products reported a quarterly profit that beat estimates, helped by its aggressive steps to resolve supply chain bottlenecks. But the backlog, combined with "macroeconomic conditions", hit demand for new products, company executives said on a post-earnings conference call. "Increase in product shipments is often leading customers and partners to absorb these shipments prior to placing new orders," Cisco CEO Chuck Robbins said. Cisco also forecast full-year revenue to rise between 10.0% and 10.5% and now expects annual adjusted earnings per share between $3.80 and $3.82.

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