Google's long-predicted payment service has finally arrived.

Called Google Checkout, the service goes live in the US today and will be available elsewhere soon.

The search giant promises users easy purchasing and the choice to keep email addresses private.

An icon for Checkout will appear next to AdWords ads for shops using the system. Merchants will also get a discount - for every $1 they spend on AdWords they can process $10 in sales through Checkout for free.

Google says there are various options for including the system on websites - from cut-and-paste buttons, to APIs that allow integration with commerce platforms such as MonsterCommerce and ChannelAdvisor.

Customers without a Google ID can create one from the merchant's site at the time of purchase.

Holders of Citi credit cards get a $5 credit for using the service.

Google Checkout's main competitor will presumably be PayPal, which has the advantage of being platform of choice on its parent site eBay. The question is whether Google's discount on transaction fees for users of AdWords will be enough of a draw.

More from Google here. ®