Donald Trump has called on the Chinese President to put more pressure on North Korea.
Speaking at a business event in Beijing, Mr Trump said China could fix the problem of North Korea.
Tensions between Pyongyang and its US-allied neighbours have been high due to the reclusive country's determination to pursue nuclear weapons.
He said: "The US is committed to the complete and permanent de-nuclearisation of North Korea.
"China can fix this problem easily and quickly and I am calling on China and your great president to hopefully work on it very hard.
"If he works on it hard, it will happen, there's no doubt about it."
The US President's words come during an official tour of Asia, which has already taken in Japan and South Korea, and been dominated by the issue of North Korea.
Mr Trump told the Chinese: "All nations must come together to ensure this rogue regime cannot threaten the world with its nuclear weapons.
"Time is quickly running out.
"We must act fast and hopefully China will act faster and more effectively on this problem than anyone.
"I'm also calling on Russia to help rein in this this potentially very tragic situation."
While in South Korea, Mr Trump had offered North Koreans a "path towards a much better future", having urged the regime to "come to the table" and "make a deal" over its nuclear programme.
"Unswervingly committed to reform"
Speaking after Mr Trump, Mr Xi did not mention North Korea but in a later speech he said China would persist with the goal of denuclearising the Korean peninsula and solving the issue through talks.
Mr Xi focused instead on China's economic progress and made a promise to be more open and transparent.
He said he would be "unswervingly committed to reform and opening up".
He said that foreign companies doing business in China would find it "more open, more transparent and more orderly".
In his speech, Mr Trump had described the trading relationship between the two countries as "very one-sided" and "unfair".
He said: "I don't blame China. After all, who can blame a country for being able to take advantage of another country for the benefit of its citizens? I give China credit.
"But in actuality I do blame past administrations for allowing this out of control trade deficit to take place and to grow.
"We have to fix this because it just doesn't work, for our great American companies and it doesn't work for our great American workers - it is just not sustainable."
Mr Trump's next stop is Vietnam on 10 November, where he will speak at the Asia Pacific Economic Co-operation (APEC) summit.
The final stop on his tour is in the Philippines.