Google announced the worldwide expansion of its pay-per-action advertising beta, a new pricing model that allows advertisers to pay only when a pre-defined action, such as making a purchase or signing up for a newsletter, is completed.

Starting today, advertisers in the beta will see an alert in their AdWords account informing them that they can now create pay-per-action campaigns. Going forward, advertisers who have enabled AdWords conversion tracking and received more than 500 conversions from their CPC and CPM-based campaigns in the past 30 days will be automatically added to the beta on a rolling basis.

Rob Kniaz, product manager for AdWords Pay-Per-Action, said the program feeds the advertisers' hunger for conversions over clicks.

"If you have some measurable action online, this is a good way to monetize it," he said.