From Google News

Apple's New York City Upper West Side retail store.

(Credit: Apple)

Apple has begun a long-awaited iPhone trade-in program at its retail stores, ahead of an event that is widely expected to include the unveiling of the new iPhone on September 10.

Apple spokeswoman Amy Bessette told CNET that the program launched Friday in Apple's US stores only. "iPhones hold great value," she said. "Customers will be able to receive a credit for their returned phone that they can use toward the purchase of a new iPhone."

She couldn't comment on a range of values Apple would ascribe to phones its customers swap for credit. CNBC said the service would give customers a trade-in value for the handset estimated at $125 for an iPhone 4, $200 for an iPhone 4S, and $250 for an iPhone 5 -- with a fresh contract. An unnamed source told The Wall Street Journal that the most Apple would be willing to credit customers would be about $280. ABC reported a figure closer to $300, also according to an unnamed source.

With Apple on the sidelines of the iPhone aftermarket for years, other trade-in options have cropped up to meet the need -- sometimes at values much higher than those being reported for an Apple program. People who want to ditch their phone when a new one comes along, without eating the full cost, found other companies willing to welcome them with open arms.

Devices traded in on sites like Gazelle and NextWorth are sold internationally in places where iPhones are very expensive. Right now, a 64GB iPhone 5 can snag a customer $370 on NextWorth.

Retailers like Best Buy and Target also offer trade-in options when new phones emerge, in addition to discounts -- like a deal this weekend at Best Buy giving iPhone 4 or iPhone 4S owners who trade in a working handset at least 50 percent off the purchase of an iPhone 5.

And, of course, there's always eBay.

With more lucrative options available, the biggest draw for an Apple program is convenience for people who buy directly through the computer maker, especially those who line up for days to be among the first to get hold of the latest iPhone.

Word of such a service cropped up in June, when Bloomberg reported that Apple was working with Miami-based trade-in company Brightstar on a program that would let consumers bring in their used iPhones for a discount on newer models and potentially for credit on other items in Apple's stores.

Next month's Apple event has the rumor mill churning out speculation at top speed, but the computer maker is generally expected to be introducing a high-end flagship iPhone, called the iPhone 5S, along with a lower-cost option, called the iPhone 5C.

Reports Monday indicated the company was close to firing up a trade-in service for its flagship smartphone. Apple was said to be preparing retail workers, giving first trainers their instructions Monday for them to start teaching other employees, and may have even started piloting the program in some stores.

Updated at 9:33 a.m. PT: with Apple confirmation and further reports of value and other trade-in alternatives.