NEW YORK, Feb 9 - Cisco Systems launched a surprisingly large $4bn debt sale on Monday, according to IFR, raising speculation that the network equipment maker was poised to make an acquisition.

The report from IFR, a Thomson Reuters service, came the same day Cisco said it would offer senior notes to help pay back $500m of debt due this month. It did not reveal an exact amount for the debt issue in a shelf registration filed with the US Securities and Exchange Commission on Monday.