Microsoft will formally offer a series of smartphones using the revamped version of its mobile operating system on the Wall Street Journal reported on Friday.

AT&T Inc will start offering these phones four weeks after the launch, which is expected to be centered in New York, with additional events in other cities, the report said.

Microsoft has been under pressure to come up with new smartphones, which controls the market with its popular iPhone, and many other companies that have launched devices using Google's Android.

AT&T will be the initial exclusive U.S. carrier for the Windows Phone 7 smartphones and will offer three handsets -- one each made by Samsung LG Electronics and HTC Corp, the report said.

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Shares of Redmond, Washington-based Microsoft were trading up 17 cents in pre-market trade. They closed at $24.49 Thursday on Nasdaq.

Microsoft shares have fallen more than 22 percent from its 2010 high of $31.58 in late April, compared with a 5 percent rise in Apple stock in the same period.