(Bloomberg) -- The top executives of Google Inc., Yahoo! Inc. and Facebook Inc.won’t attend President Barack Obama’s cybersecurity summit onFriday, at a time when relations between the White House andSilicon Valley have frayed over privacy issues.

Facebook Chairman and Chief Executive Officer Mark Zuckerberg,Yahoo CEO Marissa Mayer, and Google’s Larry Page andEric Schmidt were all invited but won’t attend the publicconference at Stanford University, according to the companies.Apple Inc. CEO Tim Cook is planning to show tothe event, where Obama is scheduled to give the keynote speech andhave a private lunch with a select group of attendees.

The technology industry had been a vital source of politicalsupport, campaign contributions and assistance in developingcutting-edge tech tactics for Obama when he won the presidency in2008 and re-election in 2012. Relations have soured since, as thecompanies have clashed with the Obama administration overgovernment spying and protecting the privacy rights of their usersand customers.