Xi also reiterated China's stance on Taiwan and called on the US to uphold the one-China policy and help to maintain peaceful development cross-Straits ties.

Obama praised the cooperation between the two countries on nuclear security, citing the example of China's new Nuclear Security Center of Excellence, a joint program between the two nations that opened in Beijing just before the nuclear summit.

"I believe we can deepen our cooperation, including against nuclear smuggling," he said.

Obama said he and Xi are both committed to the denuclearization of the Korean Peninsula and the full implementation of UN sanctions.

Assistant Foreign Minister Zheng Zeguang told reporters after the meeting that the presidents agreed to speed up negotiations on the China-US Bilateral Investment Treaty.

He added that Xi reaffirmed Beijing's stance opposing Pyongyang's development of nuclear weapons.

Jin Canrong, director of the Center for International Strategic Studies at Renmin University of China, said, "As competition between China and the US increases, meetings of the two presidents are playing a bigger role in stabilizing strategic ties, which need intense care."

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Chen Weihua in Washington contributed to this story.