US President Donald Trump has pre-empted an upcoming meeting with the Chinese President, saying America will act alone on the North Korean nuclear threat if China does not.

Key points: Trump says if China refuses to help with North Korea "it won't be good for anyone"

Trump says if China refuses to help with North Korea "it won't be good for anyone" Trump says unlike former presidents, he will not disclose how he will handle the threat

Trump says unlike former presidents, he will not disclose how he will handle the threat Former defence chief Ash Carter expresses doubts that Beijing will cooperate

Former defence chief Ash Carter expresses doubts that Beijing will cooperate US-China relations have remained uncertain since Trump's election

"If China is not going to solve North Korea, we will. That is all I am telling you," he told the Financial Times.

The comments come just days before he is set to host Chinese President Xi Jinping at his Mar-a-Lago estate in South Florida.

The two are expected to discuss a number of issues, including North Korea, trade, and territorial disputes in the South China Sea, during their meeting on Thursday and Friday.

"Yes, we will talk about North Korea ... and China has great influence over North Korea," Mr Trump said.

"China will either decide to help us with North Korea, or they won't.

"If they do, that will be very good for China, and if they don't it won't be good for anyone."

Mr Trump said trade was the incentive for China to work with the United States, but added that the US could "totally" handle the situation in North Korea without China's help.

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Asked how he would tackle North Korea, Mr Trump said: "I'm not going to tell you".

"You know, I am not the United States of the past where we tell you where we are going to hit in the Middle East."

While China provides diplomatic and economic support to its neighbour, it claims that its influence over Kim Jong-un's Government is limited.

The relationship between the United States and China has been uncertain since Mr Trump's election.

During his campaign he accused China of unfair trade practices and threatened to raise import taxes on Chinese goods and declare Beijing a currency manipulator, though it is unclear whether Mr Trump will follow through with either threat.

Mr Trump told the newspaper that he did not "want to talk about tariffs yet".

"Perhaps the next time we meet," he said.

'China is the only country that can stop North Korea': Haley

Meanwhile, Mr Trump's ambassador to the United Nations, Nikki Haley, also offered tough talk on China, telling reporters that the US was pressing China to take a firmer stand regarding North Korea's nuclear program.

UN resolutions have failed so far to deter North Korea from conducting nuclear and missile tests.

What's next in North Korea? North Korea's launch of four ballistic missiles towards Japan has unnerved the US, and it has decided enough is enough, writes Philip Williams. Read more Read more

Last year, it conducted two nuclear tests and two dozen tests of ballistic missiles.

"They [China] need to show us how concerned they are," Ms Haley said.

"They need to put pressure on North Korea. The only country that can stop North Korea is China, and they know that."

Asked what the US would do if China did not cooperate, Ms Haley said: "China has to cooperate".

Former defence secretary Ash Carter, however, said he doubted that Beijing would cooperate.

"I've been working on the North Korea problem since 1994," Mr Carter said.

"And we have consistently asked Chinese leaders ... because they uniquely have the historical and the economic relationship with North Korea to make a difference.

"They haven't used that influence, and so it's hard for me to be optimistic with that," he said.

North Korea has conducted several missile tests over the last year. ( Reuters: KCNA - file )

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