Donald Trump has said he would like to see a diplomatic resolution to escalating tensions with North Korea, but fears "we could end up having a major, major conflict".
The US president was speaking after secretary of state Rex Tillerson said China had threatened to impose sanctions on North Korea if it conducts further nuclear tests.
"We know that China is in communications with the regime in Pyongyang," Mr Tillerson said. "They confirmed to us that they had requested the regime conduct no further nuclear test."
Mr Tillerson said Beijing also told the US that it had informed North Korea "that if they did conduct further nuclear tests, China would be taking sanctions actions on their own".
China's foreign minister said the situation on the Korean peninsula "is under great tension and at a critical point".
Wang Yi said the international community must stay committed to parallel progress on denuclearisation of the Korean peninsula and upholding peace and stability.
The Trump administration has declared that all options, including a targeted military strike, are on the table to block North Korea from carrying out threats against the US and its allies in the region.
But a pre-emptive attack is not likely, US officials have said, and the administration is pursuing a strategy of putting pressure on Pyongyang with assistance from China, North Korea's main trading partner and the country's economic lifeline.
Meanwhile, Mr Trump was also reflecting on his first 100 days as president, saying he "loved" his previous life and "had so many things going".
He said his new role is "more work than in my previous life. I thought it would be easier".
The president also lamented his loss of privacy, describing life in the White House as being in "your own little cocoon".
He made his comments in an interview with Reuters, one of several to mark his first 100 days in office.
