NEW YORK (CNN/Money) - Cell phone ringtones, the snippet of songs replacing a phone's ring, are set to expand to playing a song to callers before the phone owner answers, according to a published report.

YOUR E-MAIL ALERTS Wireless Phones Asia California Deutsche Telekom AG or Create your own Manage alerts | What is this?

USA Today reported that T-Mobile Wednesday will roll out what it calls "Caller Tunes," which plays up to a 40-second song snippet to callers.

Ringtones have become so popular they have grown into a $4 billion industry worldwide, even prompting Billboard magazine to give its first "Best Ringtone of the Year" award at its annual awards show Wednesday.

An executive with T-Mobile, a unit of Deutsche Telekom (Research), told the paper the caller tunes, which will cost $1.99 per song, have the potential to be even a larger business than ringtones.

"I can assign a different song to everyone who calls me," said Michael Gallelli of T-Mobile. "That's huge."

The paper said T-Mobile competitor Verizon Wireless began testing a similar "ringback" service in two California markets last month.

Ringtone sales in the United States are a fraction of those in Europe and Asia, according to Mark Frieser at researcher Consect, which compiles Billboard's list of best-selling ringtones. Frieser expects U.S. sales of $300 million in 2004. He projects U.S. sales could grow to nearly $1 billion by 2008.