CISCO Systems Inc, the world's biggest maker of networking equipment, agreed to buy closely held Jabber Inc to add corporate messaging software.

Cisco plans to use Denver-based Jabber's functions to improve its instant message service and bolster its videoconferencing products. The San Jose, California-based company didn't disclose the terms of the agreement in a statement on Friday.

Jabber counts Wall Street firms and governments among clients for its products, which help them talk in real time over the Web.

Adding more instant features may help Cisco attract customers for its WebEx video system, which allows companies to substitute Web interaction for face-to-face meetings, Bloomberg News said.

The Jabber purchase should be completed in the first half of fiscal 2009, Cisco said.