A joint venture formed by the nation's six largest cable operators is suspending trials of its first advertising product before it even gets off the ground.

Canoe Ventures said Friday that it would discontinue plans for now to launch "community addressable messaging," which sends ads that vary by household depending on factors such as income and age.

The product has sparked privacy concerns. Privacy groups fear that the ads could lead to unwanted tracking of viewing habits and discrimination against poorer households.

Canoe cited limitations of older cable systems; one problem was that ads had to be scheduled more than a week before air date. Programmers usually set ad schedules a day in advance of broadcast.

Moreover, certain Motorola receivers would have to be upgraded for the ads to work properly. Canoe did not want to force operators to upgrade.

Confirming an earlier report by Multichannel News, Canoe said it was working on a more flexible form of addressable ads.

It still plans to introduce interactive ads in the fourth quarter, in which consumers who press a "request for information" button will receive coupons and promotional material for the product or service they are viewing.

Canoe was formed last year by Comcast Corp., Cox Communications Inc., Time Warner Cable Inc., Charter Communications Inc., Cablevision Systems Corp., and Bright House Networks L.L.C.