China and the U.S. have agreed to cooperate in their efforts to confront North Korea over their nuclear program, according to a statement released by the White House.

Politico:

Following a second day of bilateral talks, press secretary Sean Spicer said both China and the U.S. agreed to increase cooperation between the two superpowers to "convince North Korea to peacefully resolve the issue and dismantle its illegal nuclear and missile programs" and to prevent the spread of nuclear weapons in the Korean peninsula.

According to Spicer, Xi and Trump "reaffirmed their commitment to a denuclearized Korean peninsula, and committed to fully implement UN Security Council resolutions."

Trump has previously criticized China's handling of North Korea, telling Reuters in March he was "not liking" the dynamic, adding, "I know exactly what's going on between China and North Korea and everybody else."

During an interview with the Financial Times published Sunday, Trump warned that if China was unwilling to collaborate on North Korea, the United States would be willing to go it alone.

"China will either decide to help us with North Korea or they won't," he said. "If they do, that will be very good for China, and if they don't, it won't be good for anyone."

The statement may have lacked specifics, but it was significant in that it committed the US – at least temporarily – to continue cooperating with the international community in looking to blunt North Korea's drive to become a viable nuclear power. 

But Trump won't wait forever for China to apply the kind of pressure on the North Koreans everyone knows that China is capable of.  The president has already been presented with a plan to nuclearize South Korea.

The Hill:

The National Security Council has presented President Trump with options in response to North Korea's nuclear program that include placing American nuclear weapons in South Korea, NBC News reported on Friday.

Multiple top-ranking military and intelligence officials told the news source that another option presented to Trump by the National Security Council is an operation to kill the North Korean leader Kim Jong-un.

According to NBC News, both scenarios were part of a review of North Korea policy prepared ahead of Trump's meeting with Chinese President Xi Jinping this week.

Placing nuclear weapons in South Korea will be the first nuclear deployment overseas since the end of the Cold War, NBC noted. Washington withdrew all of its nuclear assets from South Korea 25 years ago.

A senior intelligence official told the network that he doubted U.S. and China could find a diplomatic solution to the crisis.

Assassinating Kim Jong-un would not be a good idea.  It would throw North Korea – a country possessing nuclear weapons – into chaos as the various factions, kept under control by brutality and fear by Kim, would be at each other's throats. 

And nuclearizing South Korea would put a nuclear hair trigger on any potential conflict on the peninsula.  So in the end, the U.S. must work with China to rein in North Korea.

How interested is China in sitting on its ally to prevent a war?  Trump is trying to tie Chinese behavior toward North Korea with trade incentives.  Whether it will be enough to move China toward denuclearizing the NoKos remains to be seen.