Cell-phone text messaging has exploded in popularity in the past few years overseas. Lovers use it to flirt; children to bully; sports fans to get scores. Employers have fired workers by text message, while for the pope it's the delivery choice for a daily thought.

In fact, the short messaging service, or SMS, generated $15 billion in revenue in Western Europe last year, according to the analysts at Strand Consult of Denmark.

Hungry for new revenue sources in a harshly competitive market, U.S. cell-phone carriers have also been working hard to get their customers to type text with their phone keypads. One set of TV ads geared at a prized demographic shows teens exchanging tart messages while standing right next to each other.

Getting Americans interested has been an uphill struggle. Yet there are signs of a warming.

U.S. phones sent 1 billion text messages last December, up sharply from 253 million a year earlier, according to the Cellular Telecommunications & Internet Association. The rest of the world sent more than 1 billion text messages a day last year, according to analysts at Telecom Trends International and French network operator Netsize.

During the spring, text messaging was boosted by a tie-in with the massively popular "American Idol" TV show. Sponsor AT&T Wireless allowed subscribers to message their votes, tallying up more than a million in the first 10 weeks of the competition.

"We're really trying to make SMS a real business," says AT&T Wireless spokesman Jeremy Pemble.

Still, the first time Synge Maher sends messages to people in the United States, it's often the first time they've ever received one.

The 27-year-old New Yorker exchanges sweet nothings like "TOTALLY MAD 4 U" with her boyfriend — a convenient and cheap way to keep in touch, she says.

She started "texting" after seeing, on a visit to London, how almost everyone in their 20s and 30s was doing it.

"They think it's so cool," she says. She finds messaging practical when she doesn't have the time to talk or doesn't want to raise her voice, as in the theater.

Maher used to have problems sending messages to friends who use other cell-phone carriers, demonstrating one of the industry's failures.

It has only been possible for about a year to send text messages between U.S. carriers. Before that, communication was largely restricted to other phones on the same carrier.

The carriers blamed differing technologies for the barrier. Others have suggested that they each tried to corner the market by "locking in" those who wanted to message each other.

Analyst Charles Golvin at Forrester Research says a big problem for U.S. carriers is that e-mail and instant messaging have become quite entrenched. Tapping out messages on a phone's keypad seems clumsy by comparison.

"A lot of people see it as a somewhat dumbed-down version of instant messaging," he says.

Another obstacle to the adoption of text messaging is that as U.S. operators are starting to promote the service, they are also charging more for it. By contrast, SMS caught on in Europe because it was cheap.

Voice calls are much more expensive in Europe than in the United States, and plans often don't include free minutes, so text messages at 20 cents each are an attractive option.

In the United States, most people have more airtime minutes than they use each month, so making another voice call often costs nothing.

Some U.S. carriers formerly included a number of free text messages each month, but that has generally disappeared.

T-Mobile USA, for instance, dropped plans this past spring that included 500 free text messages a month. While it offers 50 free incoming messages, it costs $2.99 a month to send up to 500 outgoing messages.

Golvin says the biggest obstacle is that Americans aren't used to using their phones for anything but talking.