Yahoo Starts Transition to AdCenter in North America. Yahoo and Microsoft continue the integration work required to execute on their 10-year search and advertising deal, telling North American Yahoo advertisers on Tuesday that they can begin transitioning their paid search campaigns to Microsoft AdCenter.

The companies still say that they expect to have moved Yahoo search advertisers over to AdCenter by October.

When Yahoo advertisers in the U.S. and Canada log into their accounts, they should now see an AdCenter tab where they can create a new AdCenter account or sign in using an existing account, David Pann, general manager of Microsoft's Advertising Search Network, wrote in a blog post.

Until the companies fully transition Yahoo advertising to Microsoft's AdCenter, customers will need to manage the separate accounts. After the transition is complete, they'll manage their accounts through AdCenter, Pann said.

Yahoo is offering customers a transition checklist to make sure they know how to handle the move to AdCenter.

The final stage of the transition process should begin in mid-October and be completed by the end of the month, Yahoo wrote in a blog post about the move.

However, the companies continue to caution that they won't finalize the move if they have any doubt that it could affect customers during their busy holiday sales season. "While we expect the paid search transition to be complete by the end of October, and we are on track to reach that goal, we still may consider holding off on the full integration of paid search until 2011 if we feel that the transition will in any way impact the holiday season," Pann wrote.

Microsoft and Yahoo have said that the October timeline applies to "at least the U.S.," but have said little about other regions except that the transition in Europe, Asia and Latin America may be "seamless" since the companies have existing partnerships there.

The companies reached the first major milestone in their agreement last week when they announced that Bing was fully fueling Yahoo search results in the U.S. and Canada. Authorities in the U.S. and Europe approved the deal, which calls for Microsoft to power Yahoo search and for Yahoo to use Microsoft's AdCenter, in February. At the time, they said it would take about two years to fully implement the agreement.

Nancy Gohring – Tue Aug 31, 3:20 pm ET