A leading advertising industry trade organization has just posted a letter supporting the proposed Microsoft-Yahoo partnership.

The letter from 4A's, the American Association of Advertising Agencies, was sent to the U.S. Department of Justice, which is reviewing the deal. The European Union will also be reviewing the proposed partnership.

Microsoft and Yahoo are hoping to close the deal early next year. In the deal, Microsoft's Bing would become the search engine for all of Yahoo's Web sites, and Yahoo would take over larger search advertising sales for Microsoft. Here are more details on the proposed partnership.

The two companies are partnering to gain some headway against Google, the dominant search player.

Here is the text of the letter:

"Advertising is the fuel that powers the Internet. Most websites depend on online advertising to survive – it’s what allows them to offer consumers free content and services.

"A very important form of online advertising is search advertising – the sponsored links that appear when a search engine answers a query. A healthy, competitive market for search and search advertising is crucial to the Internet’s future.

"We believe that Yahoo! and Microsoft’s proposal to combine their technologies and search platforms is good for advertisers, marketing services agencies, website publishers and consumers.

"These benefits are too important to wait for. As leading members of the advertising and marketing services industry, we urge the Department of Justice to bring its antitrust review to a speedy conclusion. This proposal enhances competition, and should be allowed to take effect as soon as possible."

It was signed by the association's president Nancy Hill and the chief executive officers of Publicis Group, WPP, Interpublic Group of Companies and Omnicom Group.