The CEOs of Google, Yahoo and Facebook have declined invitations to attend President Obama's tech summit Friday at Stanford University.
Though Apple CEO Tim Cook will be present, along with the top executives from firms like Mastercard and Bank of America, the absence of leaders like Mark Zuckerberg of Facebook and Marissa Mayer of Yahoo is notable.
Facebook, Yahoo and Google and Microsoft will send their top information security executives to the conference instead, Bloomberg reported.
Experts see the snub as evidence of ongoing tensions between the Obama administration and Silicon Valley over privacy matters, particularly in the wake of news about National Security Agency spying.
The first-of-its-kind event is designed to highlight rising cybersecurity threats and give government officials another chance to plead for more data-sharing from tech companies.
Those planning to attend include the CEOs of U.S. Bancorp, PayPal, American Express and Kaiser Permanente.
The Federal Bureau of Investigation, the Secret Service and the Department of Homeland Security will represent the government along with Obama, who is scheduled to deliver a keynote speech.