(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.

Yahoo, Facebook, Google and Microsoft Corp. said they decided tosend their top information security executives to the summitinstead.

The White House is pleased with the industry’s participation inthe summit, especially technical and engineering executives, saidan Obama administration official who asked for anonymity to discussthe event.

NSA spying

The summit is part of a renewed push to combat hackers. Panelswill focus on boosting collaboration between companies andagencies, improving cybersecurity to protect consumers and bettersecuring payment processing systems.

“It’s going to bring everybody together — industry, techcompanies, law enforcement, consumer and privacy advocates, lawprofessors who are specialists in the field,” Obama said last monthwhen he announced the summit.

The themes back up the administration’s efforts to improveinformation sharing about hacking threats and establishing anational standard for companies to report data breaches.

However, Yahoo, Facebook and Google are still reeling fromrevelations about the extent of National Security Agency spyingexposed by former U.S. contractor Edward Snowden in 2013. Thecompanies are trying to assure their users or customers that theirproducts are secure and that they don’t willingly turn over data tothe government.

Data encryption

Apple and Google have started offering smartphones that encryptdata by default, essentially shielding photos, documents andcontact lists from the prying eyes of government or hackers. Lawenforcement agencies have been trying to convince the companies tomake the data available for legitimate investigations.

The White House didn’t put any of those issues on the agenda forthe summit.

The Yahoo, Facebook, Google and Microsoft representatives willparticipate on a break-out panel at the end of the event on lessonslearned from fighting hackers.

The panel will include Scott Charney, Microsoft’s corporate vicepresident for trustworthy computing; Eric Grosse, Google’s vicepresident for security engineering; Alex Stamos, Yahoo’s chiefinformation security officer; and Joe Sullivan, Facebook’s chiefinformation security officer.

Other Obama administration officials who will attend theconference include Homeland Security Department Secretary JehJohnson, Commerce Secretary Penny Pritzker and Michael Daniel, theWhite House’s cybersecurity coordinator.

MasterCard, BOA

Along with Apple’s Cook, others who will attend the conferenceare Ajay Banga, president and CEO of MasterCard Inc.; BrianMoynihan, chairman and CEO of Bank of America Corp.; and MichaelBrown, CEO of Symantec Corp.

Obama also will announce an executive action aimed atencouraging companies to share information across industry sectors.The executive action will create a process for coming up withcybersecurity practices that the organizations should voluntarilyfollow.

It also will authorize the Homeland Security Department to enterinto agreements with the organizations to share data about hackingthreats.

Campaign contributions

Microsoft employees donated $854,717 to Obama in the 2008election cycle, and Google workers contributed $817,855 -- rankingthem fourth and sixth among all employers -- according to theCenter for Responsive Politics, a Washington non-profit that trackspolitical spending.

Yahoo’s Mayer gave Obama $2,300 in September 2007, when she wasat Google and he was trying to emerge from the shadow ofthen-Democratic presidential front-runner Hillary Clinton. Mayerfollowed up with $60,800 for the Democratic National Committee in2010, $5,000 to Obama’s re-election campaign in 2011 and a maximumcontribution of $35,800 to Obama’s “victory fund” that sameyear.

Microsoft and Google employees became the second- andthird-ranking sources of campaign cash for Obama in the 2012election, ranking only behind the University of California,according to the Center for Responsive Politics. Microsoftemployees gave his campaign $814,645 in 2012, and Google employeescontributed $801,770.

With assistance from Margaret Talev in Washington.

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