SCHAUMBURG, Ill. (AP) _ Motorola Inc. and Northern Telecom Ltd. agreed Monday to jointly sell and service cellular telephone networks throughout the Western Hemisphere.

The joint venture, called Motorola-Nortel Communications Co., is owned by the two companies and will be headquartered in the Chicago area, where Motorola is located.

Northern Telecom, based in Toronto, is a subsidiary of BCE Inc. of Montreal.

The venture does not plan to sell portable telephones to the customers of the cellular systems. Motorola, a leading manufacturer of cellular phones, will continue to sell them separately.

Motorola and Northern Telecom have been outdistanced recently by AT&T and Sweden's L.M. Ericsson, the leading suppliers of cellular telephone network equipment in the United States.

Motorola chairman George Fisher said Motorola-Nortel plans to operate in North, Central and South America, as well as in the Caribbean.