Microsoft and Yahoo are touting a brief letter that an advertising association sent to the U.S. Department of Justice supporting the search deal proposed by the companies.

"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," according to the letter, which was signed by four ad executives as well as Nancy Hill, president and CEO of the American Association of Advertising Agencies.

It says that a healthy, competitive market for search and search advertising is crucial to the Internet's future, since most Web sites depend on online advertising.

"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," the letter reads.

In addition to Hill, Maurice Levy, chairman and CEO of Publicis Groupe; Martin Sorrell, CEO of WPP; Michael I. Roth, chairman and CEO of Interpublic Group of Companies; and John Wren, president and CEO of Omnicom Group also signed the letter.

In September, Microsoft first revealed that the U.S. Department of Justice had begun seeking information for an antitrust review of the search deal with Yahoo. Under the agreement, announced in July, Bing would power Yahoo search and Yahoo would sell premium search advertising services for both companies.

The deal was nearly a year and a half in the making, during which time Yahoo rebuffed outright acquisition offers from Microsoft. There has not been much strong opposition to the final agreement.

In a statement, Yahoo said it welcomed the broad support of the deal and is hopeful it will close in early 2010.

The stated goal of the deal is to offer stronger search competition to Google, the market leader with around 70 percent market share. Combined, Microsoft and Yahoo would have around 30 percent market share.