For going on a year, Twitter's pitch to big brands and their agencies has centered on the power of promoted tweets as a complement to a TV buy. But a new ad product seems to be cutting TV out of the "Twitter + TV" lovefest.

Twitter introduced "TV conversation targeting" in the U.S. and the U.K. today, which lets marketers show ads to people who are tweeting about a given show before, during and after it runs, according to a blog post. It will be available in Twitter's self-serve ad tool, not just to bigger brands with a direct-sales relationship.

Up until now, Twitter's pitch has been about extending marketers' TV buys. "Already buying TV? Make those ads work harder with Twitter," the pitch goes. But with the new tool, Twitter advertisers can buy viewers of a show whether they're also buying ads on TV or not.

Twitter clearly thinks the tool can scale quickly. It intends to bring it to other markets, including Brazil, Canada, France and Spain, in the coming weeks.

The same result would have been possible, albeit more labor-intensive, through Twitter's keyword targeting tool -- through which advertisers can show promoted tweets to users who have tweeted the phrase "Game of Thrones," for example. But the creation of a tool to enable targeting of people who have tweeted about a show and its characters reflects a subtle shift in positioning away from the symbiotic relationship with networks that Twitter has been nurturing.

The products it's rolled out effectively make networks a partner, not a competitor. Fast-multiplying "Amplify" deals are billed as a co-selling arrangement, where networks are paid for the sponsor's pre-roll or branding within tweets sent from their handles and Twitter is paid for the promotion.

And the TV ad targeting introduced in May is offered only to advertisers who have a campaign running on national TV; the idea is that advertisers can pay to reach the same people on Twitter who are likely seeing their TV ad to drive their message home.

But not everyone can afford a TV ad, and this new option may be aimed at the have-nots. It remains to be seen whether Twitter will aggressively market it to larger spenders and effectively turn networks, which had been besties, into frenemies.