(Reuters) — President Barack Obama asked tech industry executives on Friday for closer cooperation in defending against hackers after high-profile attacks against companies such as Sony Corp. that exposed weaknesses in America's cyber defenses.

Speaking at Stanford University in Palo Alto, California, President Obama told Silicon Valley executives they needed to share more information both with each other and with his administration.

"Government cannot do this alone. But the fact is that the private sector can't do it alone either because it's government that often has the latest information on new threats," he told a gathering of CEOs.

President Obama has moved cyber security toward the top of his 2015 agenda after the recent breaches.

The Sony attack was particularly worrying for U.S. officials, who blamed North Korea for stealing data, debilitating computers and pressuring the studio to halt the release of a satirical film about leader Kim Jong Un.

"There's only one way to defend America from these cyber threats and that is through government and industry working together, sharing appropriate information as true partners," President Obama said.

He was to meet privately with a small group of business leaders in Silicon Valley to try to mend fences with tech companies still smarting over damage to their businesses when government surveillance practices were exposed by former National Security Agency contractor Edward Snowden.

Upset about the lack of reforms to surveillance programs, the CEOs of Google Inc., Facebook Inc. and Yahoo Inc. stayed away from Friday's conference.

But Apple Inc. CEO Tim Cook gave an address and other CEOs attended and spoke.

President Obama signed an executive order aimed at encouraging companies to share more cyber threat data through "information sharing and analysis organizations" — hubs where companies share information with each other and with the U.S. Department of Homeland Security.

It is one step in a long effort to make companies as well as privacy and consumer advocates more comfortable with proposed legislation that would offer firms protection from being sued for handing over customer information to the government.