However, as Beijing has remained sluggish in responding to his call for action, it seems the U.S. president still has another card up his sleeve: the South China Sea territorial dispute.
Washington, and in particular US President Donald Trump, have until very recently been critical of Beijing's cautious approach to its belligerent and nuclear-armed neighbor.
"Our task now is to hold China and others to these internationally binding obligations and to convince China's leaders to more fully exert their decisive leverage over North Korea". This became DPRK's sixth nuclear test. I applaud these tough sanctions and President Trump has done more to squeeze the North Korea's regime in a few months than the previous five administrations' efforts combined. "The urgency with which China takes it is going to be key to any successful economic pressure campaign".
Nevertheless, high-level ties have remained strong. It will be Trump's first trip to Asia and it will come just weeks after Xi Jinping is due to be anointed with a second five-year term as the leader of China's communist party. As China becomes increasingly assertive on the global stage and as ultranationalist sentiments catch fire on the domestic front, it sees "hostile forces" everywhere, from the U.S. to Japan, from the Philippines to Singapore, from India to South Korea, while Pyongyang is among the last few standing communist regimes.
"We do see Chinese policy shifting", she said.
As late as last month, Trump was still excoriating China in his intemperate tweets for "not doing enough" to isolate Pyongyang, but this week he was much more measured.
Over the last couple of months many have been concerned over the increase in tensions between the US and North Korea.
GETTYNorth Korea's military are on the move
Of special significance is China, for whom a nuclear South Korea is a greater threat than a nuclear North Korea.
China on Thursday announced [press release, in Chinese] that it would be implementing the United Nations sanctions [JURIST report] on North Korean companies by ordering them to close in China by January.
China, which provides the bulk of North Korea's energy supplies, announced on Saturday that it would cut off gas and limit shipments of refined petroleum products, effective January 1.
Why the change of heart?
As these countries are now working aggressively to improve relations with China, it is quite unlikely that they would dance to Washington's tune over the South China Sea issue like they did before.
North Korea was also on the agenda, both parties agreed that the situation in North Korea was deeply troubling.
On the same day that the Senate Banking Committee met with State Department officials at the Dirksen Senate Office Building to discuss sanctions against the isolated country, China ordered all North Korean shops within its borders to close.
Neither Vladimir Putin nor the Russian government has stated what the troops are expecting to encounter, but the Daily Mail hints at preparations for an influx of North Korean refugees, perhaps people expecting a war.