South of the city, in Tukwila, the baristas at Cowgirls Espresso wear sheer negligees and visible pink panties. It's the same story in any number of other suburban bars and drive-through stands, like the Natte Latte in Port Orchard or Moka Girls in Auburn - bikinis, racy lingerie, fetish clothing, and plenty of suggestively exposed flesh.

At Best Friend Espresso in Kenmore, at the northern end of Lake Washington, the outfits take their inspiration from Playboy-style sex fantasies. The staff will go for the naughty schoolgirl look one week, then don black-framed glasses the next to look like sexy secretaries.

Welcome to "sexpresso" - the latest coffee fad to hit America, in which the country's seemingly boundless fascination for Italian-style Java is combined with its equally boundless fascination for half-naked women.

Seattle may not be the first American city to come to mind when it comes to the pleasures of the flesh, but it is super-saturated with coffee stands, all of which are battling each other - and the mighty, locally based behemoth that is Starbucks - to give morning commuters an extra reason to stop off at their particular establishment.

"Here on Aurora Avenue, there's a drive-through every 20 blocks. You have to do something to stand out," said Sarah Araujo, owner of The Sweet Spot. Ms Araujo brainstormed with her customers to come up with something new and different when she bought the cafe - then called Aurora Espresso - a couple of years ago.

Not only did her staff start removing clothing and giving suggestive new names to the drinks, they also started doing theme days - Tube Top Tuesdays, Wet T-Shirt Wednesdays and Fantasy Fridays.

The plastic coffee cups are indistinguishable in shape from those sold in any other coffee shop in north America. But they are decorated with the silhouette of a busty naked woman carrying a steaming mug of "Joe". The lid is sealed with a pink lipstick kiss.

During the summer, when the persistent Seattle rain finally lifts and the Pacific Northwest enjoys a few months of real sunshine, The Sweet Spot organises bikini car washes and takes care to post the most suggestive photographs on its website. This year, the cafe is planning a barista calendar.

Coming with a theme for a coffee bar is nothing new in America. In Los Angeles, there are cafes where you can buy second-hand books, get cut-price legal advice, throw pots, or listen to really, really bad live music provided by local bands. Strangely, nobody until now has thought of combining coffee with sex.

Ms Araujo and others say it has given an unmistakable boost to their businesses. Their staff may only receive minimum wage, but the tips can be terrific.

"Our customers may be half-asleep when they get here, but we do what it takes to wake them up," said Ms Araujo. "They always say: 'Thanks for the great cup of coffee and the smile; it made my day'."

Some local puritans have expressed disquiet - and railed at The Seattle Times newspaper after it ran a feature on the sexpresso trend 10 days ago. But law enforcement officials say there is nothing illegal about wearing scanty clothing, so the trend is almost certain to keep spreading.

Even Seattle, though, has its limits. Sexy underwear is all very well, but the city hardly has the climate of French Polynesia.

"We're not in bikinis right now," Ms Araujo conceded in the murky early hours of yesterday. "We're going more for miniskirts and boots. It's pretty cold up here."