Donald Trump has fired the first shot.
North Korea will be at the centre of Trump's discussions with Chinese President Xi Jinping when the two leaders meet on Thursday for the first time.
Xi is travelling to the US state of Florida where Trump will host him at his Mar-a-Lago resort for two days.
North Korea's actions have caused anxiety not just in Washington but also among its allies in Asia, such as Japan and South Korea.
Reclusive, communist North Korea is accused of building a nuclear arsenal and long-range missiles capable of hitting US cities.
Since taking office in January, Trump has promised to take a hard-line with North Korea. He has often said his policies would be tougher than his predecessors.
Trump has even said the US is prepared to take on North Korea on its own, even if China doesn't help.
With or without Beijing
In comments that were designed to put pressure on China, Trump said that the US might take unilateral action if diplomacy failed. The interview was published on Sunday.
"Totally," was Trump's response when asked if he could deal with North without China's help.
North Korea has conducted five nuclear tests between 2006 and 2016, two of them just last year.
Washington is concerned that the country could very soon acquire the ability to mount nuclear warheads on long-range missiles and US officials say North Korea could possibly become capable of hitting the US with such missiles by the end of Trump's four-year term.
Others, such as Siegfried Hecker, the former director of Los Alamos National Laboratory in the US, say it would take at least five years.
Trade as leverage
Trump has been persistent in his view that the US faces a disadvantage with its trading partners, especially when it comes to the largest – China.
He decries the huge trade surplus that China has built by exporting more goods to the US than it imports.
Trump says the US could increase the tax on Chinese imports, something that could tilt the trade balance in favour of the US and, in his view, give Washington an opportunity to arm-twist Beijing into taking a tougher line on North Korea.
"I think trade is the incentive. It is all about trade," Trump said in the interview when asked how he could convince China to listen to US demands.
Besides the well-timed interview, Trump just last Friday signed two executive orders aimed at investigating possible abuses caused by large US trade deficits and stopping import duty evasion.
That move instantly drew reaction from Beijing, which said any trade enforcement measure must comply with international trade rules.
China's influence over North Korea
China is North Korea's closest ally and largest trading partner.
Beijing often backs Pyongyang at the United Nations by making sure the strong sanctions-language is toned down.
Chinese exports of machinery, food and fuel help sustain the North Korean economy to a large extent.
But stability in North Korea also works in favour of China, which fears a large influx of refugees if things get any worse in its neighbouring country.
The US is pushing for the toughest sanctions on North Korea yet. And this can't be done without the Chinese.
Trump's national security aides have completed a review of US options to try to curb North Korea's nuclear and missile programme.
The recommendations include economic and military measures but leans more toward sanctions and increased pressure on Beijing to rein in its neighbour, a US official said.
While it remains unclear what kind of sanctions are in the offing, US officials have indicated they might pressure Chinese companies and businessmen to cut ties with North Korea.
Although the option of preemptive military strikes on North Korea is not off the table, the review prioritises less risky steps and "de-emphasises direct military action," the official added.
South China Sea
Trump and Xi are also expected to discuss Chinese ambitions in the South China Sea, through which about $5 trillion in ship-borne trade passes every year.
China claims most of the resource-rich South China Sea, while Brunei, Malaysia, the Philippines, Taiwan and Vietnam also have claims on the strategic waterway.
For China, the US is an intruder when it comes to this dispute.
But Washington says it won't allow China to build military bases on islands that are in international waters.