Salesforce.com Inc and Oracle Corp engaged in a public spat over a keynote speech on Wednesday, highlighting the software companies' increasingly bitter rivalry.

Salesforce.com Chief Executive Marc Benioff sent out a statement that said Oracle had just canceled his speech at the Oracle OpenWorld conference and advertised an alternative venue where he said he would make a speech and take questions.

But a source at Oracle who asked not to be named, denied Benioff's claims, saying that Oracle told Salesforce.com it had to move the speech to 8 a.m. October 6, from 10 a.m. October 5, to make room for an Oracle customer event that needed a bigger venue because it was oversold.

Benioff said he would instead speak on October 5 at a restaurant in the St. Regis Hotel in San Francisco and then hold a press conference immediately afterward.

Oracle just canceled my keynote tomorrow. But the show must go on! Everyone is welcome to join me at Ame Restaurant tomorrow to hear about the social enterprise. Sorry Larry, the cloud can't be stopped, Benioff said.

Salesforce.com sells Web-based business management software that competes with Oracle products.

Salesforce.com shares were down $2.14, or 1.8 percent, at $115.46 in morning trading on the New York Stock Exchange, but it was not immediately clear if the stock move was related to the public dispute.

(Reporting by Jim Finkle, Writing by Sinead Carew; editing by Gerald E. McCormick and Maureen Bavdek)

Marc Benioff Salesforce Oracle Keynote