** Microsoft's MSFT.O shares rise after OpenAI said it would start showing ads in ChatGPT to some U.S. users as part of efforts to ramp up revenue
** MSFT is up 1.28% at $462.52 and is set to snap four straight sessions of losses
** The ads will be tested with users on the company's free tier and the lower-priced Go plan that it is now expanding globally, OpenAI said on Friday. They will show up in the coming weeks and will be separate from the answers generated by ChatGPT
** MSFT owns about 27% of OpenAI, which is reportedly valued at around $750 bln
** Among 60 analysts covering MSFT, avg rating is "buy" and median PT is $630 - data compiled by LSEG
** MSFT is down 4.3% YTD vs NASDAQ Composite Index's .IXIC 1.3% increase.
(Reporting by Chibuike Oguh in New York)
((Email: Chibuike.Oguh@thomsonreuters.com; Phone: +332-219-1834; Reuters Messaging: chibuike.oguh.thomsonreuters.com@reuters.net))
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