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Wal-Mart's head of U.S. online marketing leaves for startup

April 7 (Reuters) - The head of marketing for the U.S. online business of Wal-Mart Stores has left the retailer to return to a business-conference firm he founded, a company statement said on Thursday.

The departure of Brian Monahan after three years at Wal-Mart was announced by NewCo, the startup he helped launch in 2012 in San Francisco with media industry veteran John Battelle. A spokesman for Wal-Mart, the world's largest retailer, confirmed that Monahan's last day was April 1.

"We're thankful for the great contributions Brian made to the business and wish him the best with NewCo. We're in the process of identifying a successor," Wal-Mart spokesman Dan Toporek said.

In the statement Monahan said he was "compelled to dive back in and help" the management team at NewCo, citing the momentum of the business and the launch of new editorial products. Monahan's title is "Chief Evangelist".

NewCo holds its conferences inside the offices of start-ups in various cities around the world, attempting to offer something different than traditional business seminars and introduce up-and-coming companies to investors and entrepreneurs.

Monahan joined Wal-Mart in 2013 as Vice President of Marketing for the website. In that role he was in charge of the overall online marketing strategy.

In December, Wal-Mart rejigged the top of its marketing team, with Tony Rogers, formerly head of marketing in China, becoming chief marketing officer, replacing the retiring Stephen Quinn. The retailer also brought in former Target Corp CMO Michael Francis as a consultant, a move that was seen by some observers as a sign it was looking to tweak its marketing approach.

Wal-Mart's online sales growth has slowed in recent months, going from 17 percent in the first quarter of the last fiscal year to 16 percent in the second, 10 percent in the third and 8 percent in the fourth quarter ended on Jan. 31.

Wal-Mart has attributed the drop-off to weakness overseas, including in China and Brazil, and says that its online business in the United States has been good. The company does not disclose a detailed breakdown of sales in each market.

(reporting by Nathan Layne in Chicago; editing by Grant McCool)