If you wondered when Google might begin offering pay-per-call ads, or at least click-to-call, it looks like the time is now.

In a very thorough blog post, Greg Yardley reports (nice work Greg, screen caps, too) that Google has started to test click-to-call ads. No word if the test is limited to only the US or if advertisers are paying and being listed on a pay-per-call basis or if this is an add-on to paying by the click. Yardley's post also points to a Google Click-to-Call FAQ that offers a few more details about how the system works:

We're testing a new product that gives you a free and fast way to speak directly to the advertiser you found on a Google search results page ? over the phone.

Here's how it works: When you click the phone icon, you can enter your phone number. Once you click 'Connect For Free,' Google calls the number you provided. When you pick up, you hear ringing on the other end as Google connects you to the other party. Then, chat away on our dime.

We won't share your telephone number with anyone, including the advertiser. When you're connected with the advertiser, your number is blocked so the advertiser can't see it. In addition, we'll delete the number from our servers after a short period of time.

Am I charged to connect to an advertiser?

No. Google foots the bill for all calls - local and long-distance. However, if we call a cell phone number, you may incur airtime fees depending on the cell phone plan. Check your cell phone provider for details.
[SNIP]
In addition, we only store your information (including your phone number, date, time, and call length) temporarily for no longer than 4 months after the last time you used the service.

There is also a click-to-call privacy FAQ.

Note: I tried the same search as shown in Greg's post and did not get any pay-per-call options. I tried several other searches and came up empty on all occasions.

The screen caps show AdWord listings with a green telephone icon located next to them. When the user clicks the icon, a box appears where the user enters their phone number (and also decide to save the number on their computer for future click-to-call sessions and according to the FAQ, "other Google services, such as our mobile services." It's stored via an encrypted cookie on your computer.

Also worth noting that the Google's click-to-call connectivity comes from an unamed third party vendor.

About a month ago, Danny and others blogged about Yahoo starting to test pay-per-call in the U.S. using Ingenio?s technology. Ingenio also powers AOL's pay-per-call program that Chris wrote about earlier this year. Yahoo launched pay-per-call in the UK in August.

Want to discuss? Check out the SEW Forums thread: Google Begins Testing Click to Call Advertising

Postscript: I checked to see if Google had already trademarked/service marked the phrase, "Click-to-Call." Found nothing. Similar spellings are registered. CLICK2CALL is registered to a mortgage company in New York while CLICK-2-CALL is registered to VoIP provider, Vonage.

Click to Call Ads can put customers on the phone with you the moment they see your Ad on the net. Web users click your ad and enter their phone number. Our System calls them instantly and puts them on the line with your business or call center. You pay only when a call is made, at the price you set - - no long distance or other phone charges. Click to Call Ads participate in the same Ad auction as text ads, and receive the same ad discounting benefits. Your ad will compete with all other ads for position on search results pages. You are charged for a Click to Call Ad only when a user enters his or her phone number and is connected with your call center for at least 10 seconds. (This ’10 second rule’ protects you from mistaken calls, hang-ups, and other errors.) Approx costing involved for the above keywords would be a total of $2500/month to start with any three Continents of your choice namely: America, South America, Australia, Europe, Africa, and Asia.