American Express Co. had been reported to compete for an equity stake in Foursquare Labs. This was after speculations of Microsoft Corp's planned stake acquisition in the social media startup, said people familiar with the matter.

Microsoft and American Express were said to compete for an investment in Foursquare. Sources also added that the two companies would not cooperate on a joint bid. Sources asked not to be named as the information is not yet public. Foursquare had been in talks with different companies about a possible investment and might lead to a deal.

Jon Steinback, an executive in New York-based Foursquare had no comment regarding the discussions with potential investors. American Express' spokeswoman Leah Gertsner said that the company would not comment regarding rumors and speculations.

Foursquare pulled in USD2 million sales last year and had continued to introduce new advertising products. The company was valued at USD600 million by investors who have waited for the company to deliver its promises.