The US will take unilateral action to eliminate the North Korean nuclear threat if China does not help bring pressure to bear on Pyongyang, US President Donald Trump has warned.

Trump, who will meet Xi Jinping, the President of China, for the first time on Thursday, said the US would go it alone if Beijing refuses to co-operate.

However, he refused to say whether that implied taking military action against the hermit dictatorship.

"China has great influence over North Korea. And China will either decide to help us with North Korea, or they won't," Trump said in an interview with The Financial Times.

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

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

Conventional thinking is that China would have to take a lead role in imposing further sanctions on the regime in Pyongyang because of its economic leverage.

Trump has been deeply critical of China in the past, especially its trade policy. However, he said he hoped that would not stand in the way of a deal being reached at the summit with Xi at his Mar-a-Lago resort in Florida this week.

"I have great respect for him. I have great respect for China. I would not be at all surprised if we did something that would be very dramatic and good for both countries and I hope so," he told the paper.

Nikki Haley, the US ambassador to the UN, also issued a stark warning, saying America would "no longer take excuses from China".

Haley said: "They need to show us how concerned they are. They need to put pressure on North Korea. The only country that can stop North Korea is China, and they know that.

"China has to co-operate. This is now down to: 'Do we want to continue to see these ballistic missile attacks from North Korea, or does China want to do something about it?' "

She spoke as the US took over the rotating presidency of the UN Security Council.

She added: "We're going to say what we think, and we're going to move the ball and that's what this is about."

Concern has been mounting about the North Korean missile program in the US for some years.

During the handover of power, the administration of former US president Barack Obama identified North Korea as the top national security issue for the Trump administration.

Some US security officials believe the regime of North Korea's leader Kim Jong-un might have a nuclear-armed missile capable of hitting the United States within four years.

South Korean intelligence warned last month that another nuclear test by the North was imminent, with analysts suggesting Pyongyang might seek to "overshadow" the US-Chinese summit in Florida with a show of force.

South Korean government sources told the Korea JoongAng Daily that preparations at the North's Punggye-ri nuclear proving grounds would be completed before the weekend.

Last month, North Korea fired a missile into the sea off the east coast of the Korean peninsula just as Trump was hosting Shinzo Abe, the Japanese Prime Minister, at Mar-a-Lago.

Rah Jong-yil, a former head of South Korean intelligence, told the Telegraph that China could tackle the issue "very easily by closing the border entirely and completely strangling all business and economic traffic between the two countries".

Last week, US senator John McCain said only Beijing could control Kim, whom he branded a "crazy fat kid".

McCain told MSNBC earlier this month: "China is the only one that can control Kim Jong-un, this crazy fat kid that's running North Korea. They could stop North Korea's economy in a week."

On Thursday, Trump had warned the summit would be "very difficult".

He said: "The meeting next week with China will be very a difficult one in that we can no longer have massive trade deficits and job losses. American companies must be prepared to look at other alternatives."

The summit is taking place at Mar-a-Lago, Trump's palatial club in Florida, which has been called the "Winter White House".

His son-in-law and senior adviser Jared Kushner has emerged as a key architect of the summit along with Cui Tiankai, the Chinese ambassador.

The two men chose Mar-a-Lago as the venue and have reportedly worked closely on crafting a joint statement the two leaders will deliver.

Kushner and his wife Ivanka, Trump's daughter, were said to have been invited to the Chinese embassy in February.

Ash Carter, US Defence Secretary under Obama, said he doubted Beijing would co-operate.

He said: "I've been working on the North Korea problem since 1994 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."

Carter, speaking on Sunday shortly before Trump's comments, warned a US pre-emptive strike against North Korea's nuclear weapons risked triggering an invasion of South Korea.

"I'm confident of the outcome of that war, which would be the defeat of North Korea," he said. "But I need to caution you, this is a war, an intensity of violence associated with it, that we haven't seen since the last Korean War.

"Even though the outcome is certain, it is a very destructive war so one needs to proceed very carefully here."

Trump said he believed Brexit would be a "great deal" for the UK and also " really good" for the European Union.

His view on whether other countries would leave the EU appeared to have moderated, and he now believed they were less likely to.

He said Europe seemed to be "really holding" and had done a "better job" since the UK voted to leave.

Telegraph, London