In the radio ad, a talking faucet extols Miami-Dade's tap water as cheaper, purer and safer than bottled water.

It may have sounded innocuous to most listeners, but the 30-second spot left the nation's largest purveyor of bottled water boiling mad.

Nestle Waters North America, which makes nearly $4 billion a year selling Zephyrhills and other brands, is threatening to sue if the county doesn't kill commercials the company brands as false advertising.

''It's an attack on the integrity of the company,'' said Nestle spokesman Jim McClellan. ``It's an attack on the product we produce - and it's blatantly wrong.''

With the ads ending a five-week run last month and no plans to revive it, the county considers the legal issues moot. But John Renfrow, director of the Water and Sewer Department, defended the county's right to tout its tap water. ''Basically, the message is that our water is fine,'' he said. ``It's wonderful. It's delicious. This is just one of many different spots we've done.''

Environmentalists blasted the threat against the state's largest utility - believed to be a first - as a warning shot from an industry worried about slow sales after years of gushing growth.

''Nestle should be ashamed for harassing Miami for promoting its own water,'' said Wenonah Hauter, executive director of Washington-based Food & Water Watch. ``This is just outrageous. It's just a way to scare off other utilities.''

McClellan said Nestle - which contacted The Miami Herald to publicize its complaint - has never challenged utilities hawking tap water as cheap and safe. But Miami-Dade, he argued, had stepped over the line in besmirching bottled water.