EBay plans to announce today that it has hired Google to sell advertising that will appear on many pages shown to users outside of the United States.

The deal is noteworthy not only because the two companies are increasingly in direct competition — in areas like online phone service, payment and product listings — but also because eBay signed a similar partnership in May with Yahoo that included ads on domestic pages. That alliance was seen as a way to counter the growing power of Google.

Google is the leader in selling text advertisements on the Internet. In this business, it dwarfs Yahoo, especially in Europe. So as eBay looks to build its international advertising revenue, Google was in a position to offer a better deal than Yahoo.

“Google is very strong in every country outside of the United States,” said Meg Whitman, eBay’s chief executive, in an interview Sunday night. “We felt this arrangement of assets made sense.”