The top executives of Cisco Systems and Microsoft said yesterday that they would ensure their products work together, seeking to prevent customers from putting off buying decisions.

While Cisco and Microsoft are undisputed leaders in their respective fields of network equipment and software, they are competing aggressively to deliver a single, "unified communications" system that ties together e-mail, phones and other tools over internet networks. In their first joint public discussion, Cisco chief executive John Chambers and Microsoft chief executive Steve Ballmer said they would compete in some areas, but also meet demands from customers who want to pick and choose from both.

"They're saying, 'Give me the choice. Don't give me the all or nothing choice'," Mr Ballmer said, adding that he was seeking "respectful competition" with Cisco. "There are plenty of competitors that you just don't talk to, or things get acrimonious," Mr Ballmer said.

"That's not where we want to go with Cisco," he added.

Mr Chambers said he and Mr Ballmer would visit customers together later in the day, and that they would try to clarify how the two companies compete and work together at the same time.

"Even where we're going to compete, what the customer wants to know is, 'Tell me how to interoperate. Don't make me throw away one relationship because of the other'," Mr Chambers said.

The comments come as both companies launch new products and form alliances that point to a growing rivalry.

Microsoft and network equipment maker Nortel Networks, a Cisco competitor, announced a broad alliance in unified communications last year.