A day after shutting down most of its U.S. shops for three hours to retrain baristas on espresso basics, Starbucks is welcoming customers back Wednesday with a new promise posted in stores: "Your drink should be perfect, every time. If not, let us know and we'll make it right."

Starbucks Chairman and Chief Executive Howard Schultz said the 135,000 baristas who got the refresher course pledged to uphold "the uncompromising standards and quality that have made Starbucks the world's coffee leader."

Nearly 7,100 company-operated Starbucks stores across the U.S. — all except the licensed shops in supermarkets, airports, malls, hotels and the like — closed at 5:30 p.m. local time Tuesday for a teach-in that was part espresso tutorial, part pep rally.

Instead of dumping shots straight into the paper cups they'll serve to customers, Starbucks baristas are getting back to pouring espresso into shot glasses first. "You get to see if it's a quality shot of espresso," store manager Justin Chapple, 25, said during a training session at a New York City store.

Starbucks switched to automatic espresso machines years ago, but it still takes skill to work them. Baristas have to adjust the grind to make sure a shot doesn't pour too quickly, making it watery, or too slowly, making it bitter.

"It's not as simple as pushing a button," said Ann-Marie Kurtz, Starbucks' manager of global coffee and tea education.

Starbucks wouldn't disclose how much revenue it stands to lose during the shutdown, but analysts say the financial impact will be negligible compared to charges the company will take as it closes about 100 poorly performing U.S. stores this year and pays severance to more than 200 corporate support staff it laid off last week.

U.S. stores make up the bulk of Starbucks' revenue, which totaled $9.4 billion in fiscal 2007, when the company earned more than $672 million.

Robert Toomey, an analyst with E.K. Riley Investments, said he didn't expect a surly backlash from customers getting turned away. "It's a low-traffic time of day," he said. "The risk of ticking off customers is pretty minimal."

It makes sense to tackle the training in one fell swoop, and it shows the company — which has seen its stock slide about 50 percent since late 2006 — is committed to turning itself around, Toomey said.

"They know they've fallen short," Toomey said. "The quality of the product has deteriorated a bit over the last few years, and they know they've got to improve it."

Christina Mallozzy, a pharmaceutical saleswoman, looked miffed when she walked up to a Starbucks on Manhattan's Upper East Side only to find out it was closed. "I'm not furious. My life's not going to end," said Mallozzy, 25. She was, however, annoyed because she had she had gone to the trouble of snagging a parking space.

Meanwhile in Seattle, a line a dozen people deep snaked outside one of Caffe Vita Coffee Roasting Co.'s Seattle shops at dusk Tuesday, as the local chain gave away free espresso drinks while the world's largest gourmet coffee retailer shut its doors.

"Free-market economy, baby! You've got to take advantage of what the competition throws at you," squealed Amy Grooms, a 29-year-old accountant who said she quit going to Starbucks once she moved to Seattle, because she thinks independents brew better-tasting coffee.

Other rivals offered similar deals. Dunkin' Donuts slashed the price of its small lattes, cappuccinos and other coffee drinks for 99 cents for most of the day. Yet spokeswoman Michelle King demurred when asked if it was a competitive jab at Starbucks.

"We are offering this promotion today because there is an opportunity to reach a large number of coffee drinkers, as well as provide our own loyal customers with a great deal," King said in an e-mail to The Associated Press.

McDonald's Corp., which has been trying to steal Starbucks customers by revamping its coffee menu, declined to comment on Starbucks' training effort and offered no special deals Tuesday.

Starbucks plans to train its international employees over the next month, as well as baristas who work at the company's more than 4,000 licensed shops.