US President Donald Trump has said the United States will "solve" the nuclear threat from North Korea, with or without China's help.
"If China is not going to solve North Korea, we will. That is all I am telling you," he said in an interview with UK newspaper the Financial Times.
Pressed on whether he thought he could succeed alone, he replied: "Totally."
Mr Trump was speaking ahead of a scheduled visit from Chinese President Xi Jinping this week.
"China has great influence over North Korea. And China will either decide to help us with North Korea, or they won't. And if they do that will be very good for China, and if they don't it won't be good for anyone," Mr Trump told the FT.
Asked if he meant "one-on-one" unilateral action, Mr Trump said: "I don't have to say any more."
He did not give any further details on what action he would take.
Mr Trump's brief comments, published just days before the key meeting with Mr Xi at Mr Trump's Mar-a-Lago resort in Florida on Thursday, are the latest in a series of warnings over North Korea's nuclear development.
There are fears that Pyongyang could eventually develop the ability to launch long-range nuclear missiles capable of striking the mainland US.
During a trip to Asia in March, US Secretary of State Rex Tillerson said pre-emptive military action was an option "on the table".
A month earlier, Defence Secretary James Mattis warned that any use of nuclear weapons would be met with an "overwhelming" response.
However, it is generally thought that military action against North Korea would lead to very high military and civilian casualties.
US officials stress that contingency planning for the military option has been discussed for decades, but the preferred course of action remains pressing North Korea to abandon its weapons programmes via sanctions and other diplomatic pressure.
The United Nations and several nations already have sanctions in place against North Korea, targeting its weapons programme and financial ability to function abroad.
Meanwhile food aid to North Korea - which relies on donations to feed its people - has fallen in recent years as tensions have risen.
But these measures do not appear to be slowing down North Korea's ability to move forward on the military front.
It is argued that sanctions that targeted the intermediaries that keep North Korea moving - like Chinese banks - would make a real