Oracle Corp. has made an unsolicited $5.1 billion bid for PeopleSoft Inc., a deal that, if accepted, could derail PeopleSoft's recently announced agreement to buy another software provider, J.D. Edwards & Co.

Oracle said it is offering $16 a share cash for PeopleSoft. That represents slightly less than a 6 percent premium over PeopleSoft's Thursday closing price of $15.11 a share, down 9 cents on the day. Shares o PeopleSoft shot up to $19 in pre-market trading immediately after Oracle's announcement.

Oracle said that it if completes the deal for PeopleSoft, it would reexamine whether to go ahead with the proposed $1.7 billion stock purchase of J.D. Edwards.