WASHINGTON -- Cyberespionage for economic gain by China is putting "enormous strain" on U.S.-China relations and needs to stop, President Obama's national security adviser said Monday.

Susan Rice was speaking on relations between the two world powers at George Washington University ahead of a high-profile state visit this week by Chinese President Xi Jinping.

Rice urged China to join the U.S. in promoting responsible forms of state behavior in cyberspace. She said it would be a "critical factor" in determining trajectory of U.S.-China ties.

Get Breaking News Delivered to Your Inbox

"This isn't a mild irritation; it's an economic and national security concern to the United States. It puts enormous strain on our bilateral relationship," Rice said.

Hacking attacks on U.S. companies and government agencies have become a growing source of tension ahead of the visit by Xi, who will meet Mr. Obama on Friday.

"We want a business climate where intellectual property rights and trade secrets are respected, not stolen," Rice said.

China is suspected in the recent theft of personal data of millions of current and former U.S. government employees. The U.S. has not publicly blamed China for that breach. Experts suspect it was designed to gather intelligence rather than for commercial gain.

Rice's overriding theme was a familiar one: The U.S. wants to cooperate with China on tackling global concerns, but China should abide by global norms - in economic policy, its security policy and behavior in the disputed seas of East Asia and in human rights.

"This is a vital relationship of the 21st century, and we have to be upfront about our differences, because they are preventing us from reaching the full potential of our cooperation," she said.

Referring to the South China Sea, where China has spooked its neighbors by building artificial islands with military facilities to assert its disputed territorial claims, Rice asserted that the U.S. "will sail, fly and operate anywhere that international law permits."

But Rice noted that confidence-building measures by the U.S. and Chinese militaries agreed last year have reduced the risk of "unintended incidents" between the two forces in the Asia-Pacific - where China is emerging as a challenge to decades of U.S. pre-eminence.