President Barack Obama pushed Chinese leader Xi Jinping to do more to address the online theft of U.S. intellectual and other property coming from his country and said the hacking is “inconsistent with the kind of relationship we want to have with China,” a top White House aide said.

Obama national security adviser Tom Donilon said discussion of cybersecurity took up much of the Saturday morning meeting between the two leaders, which ended with few policy breakthroughs but the prospect of stronger personal ties.

Donilon said Obama described in detail instances of hacking against U.S. companies by entities in China and said the U.S. didn’t have any doubt who was behind them.

“The president underscored that resolving this issue was really key to future economic U.S.-China relations,” Donilon told reporters after about eight hours of meetings Friday and Saturday. The gathering at the sprawling Sunnylands estate was their first meeting since Xi took office in March.

Obama “asked that the Chinese government engage on this issue and understand that if it’s not addressed, if it continues to be this direct theft of United States property, that this was going to be very difficult problem in the economic relationship and was going to be an inhibitor to the relationship really reaching its full potential.”

Xi’s senior foreign policy adviser, Yang Jiechi, told reporters that cybersecurity shouldn’t be the cause of friction but an area of cooperation for two nations that face similar challenges. Yang said China “is against all forms of hacking and cyberattacks. China itself is also a victim of cyberattacks and we are a staunch supporter of cybersecurity.”

Yang said the two leaders “blazed a new trail” away from the two nations’ past differences in the summit and “talked about cooperation and did not shy away from differences.”

“We have to stay each other’s partners, not rivals,” Yang said.

Donilon also said the leaders found “quite a bit of alignment” on the subject of North Korea and “agreed that North Korea has to be denuclearized and that neither country will accept North Korea as a nuclear-armed state.”

The leaders left the final remarks on the summit to their aides and closed the summit in low-key style, with no formal statements to the press, just a private tea with Xi’s wife.

The White House said in a statement shortly after Xi departed the estate that the two nations agreed to work together for the first time to reduce hydrofluorocarbons, a potent greenhouse gas. The agreement was cast as a significant step toward tackling climate change.

U.S. officials are hoping that Xi, who took office in March, proves to be a new type of Chinese leader. He has deeper ties to the U.S. than his predecessors, given that he lived in Iowa briefly as a visiting official and sent his daughter to college in the U.S.