Now, as South Korea's president arrives at the White House, Trump appears to be coming to terms with the reality. China has yet to apply the kind of serious pressure on North Korea that might prompt the rogue regime to tamp down its nuclear and ballistic missile activity -- and he is looking to chart the next phase of the US' efforts to put a stop to those North Korean programs.
Top Trump administration officials on Wednesday warned publicly and privately that the US is nearing an inflection point in its efforts to pressure North Korea into abandoning its bellicose behavior, suggesting that Trump might seek to crank up diplomatic and economic pressure on China -- which accounts for nearly 90% of North Korea's foreign trade.
"There's recognition that there has to be more pressure on the regime. I think what you'll see in the coming days and weeks are efforts to do that," Trump's national security adviser H.R. McMaster said Wednesday in public remarks at a national security conference, noting that "the threat is much more immediate now."
McMaster's remarks came just a couple hours after a senior White House official warned that China is "falling far short" of the level of pressure it could be applying to North Korea and told reporters in a briefing Wednesday that Trump has asked his administration to draw up a list of new sanctions for him to consider.
On Capitol Hill, Senate Foreign Relations Committee Chairman Bob Corker emerged from a meeting Wednesday with the administration's special representative for North Korea policy sensing that the administration was readying sanctions against China.
"The takeaway is China is still not doing what China needs to be doing, and while we're working with them in a very cooperative way right now, my sense is if they don't step up soon we're going to then move to the coercive mode, which means secondary sanctions," Corker said.
The Trump administration in March slapped sanctions against several Chinese businesses and individuals, but could issue far wider-reaching sanctions on Chinese companies and industries that do business with North Korea in a bid to push the Chinese government to more forcefully pressure North Korea into changing its behavior.
And even as Trump administration officials stressed that a stepped up campaign of diplomacy and economic pressure remains the administration's preferred strategy, Trump is also keeping military options on the table.
The US military recently updated those options
, which are now ready to be presented to Trump in the event North Korea conducts an underground nuclear test or ballistic missile test that would signal a threat to the US, two military officials told CNN on Wednesday.
"What we have to do is prepare all options because the President has made clear to us that he will not accept a nuclear power in North Korea and a threat that can target the United States and target the American population," McMaster said.
The US is weighing more aggressive efforts after US Secretary of State Rex Tillerson and Defense Secretary James Mattis held a summit with their Chinese counterparts last week and as Trump has publicly shown signs of frustrations with the current approach -- with a focus on the role he had hoped China would play.
"I wish we would have a little more help with respect to North Korea from China, but that doesn't seem to be working out," Trump said last week after tweeting that the Chinese campaign to pressure North Korea -- however limited -- "has not worked out."
The issue also returned to the fore amid renewed attention to the North Korean regime's activities following the release and subsequent death of Otto Warmbier
, an American student who fell into a coma during his year-long imprisonment in North Korea.
The senior White House official who briefed reporters Wednesday on the condition of anonymity said Trump remains "determined to follow through" on the US' efforts to crank up the diplomatic and economic pressure on North Korea.
"The campaign is only now really gathering momentum," the official said. "There is plenty more pressure that could be brought on North Korea."
But experts who have closely watched the new administration's effort to encourage China to weigh heavier pressure on North Korea have long predicted Trump and his advisers would eventually hit a wall -- just as past administrations have in similar efforts to elicit stronger cooperation from the Chinese on the North Korean nuclear issue.
"After six months of a policy review and reinventing the wheel, they've basically arrived at exactly the point the Obama administration left off," said Ely Ratner, a senior fellow in China studies at the Council on Foreign Relations who served as Vice President Joe Biden's deputy national security adviser.
"The question for me all along was, 'When is Trump going to realize that Xi Jinping is not going to deliver for him and when he realizes that, what is his response going to be?' The former has happened and now we're awaiting to see -- does this mean he pulls off the gloves?" Ratner added.
All roads appear to lead to China.
Trump appeared encouraged by China's initial show of pressure on North Korea: Beijing banned imports of coal from North Korea in late February and Trump signaled that Chinese President Xi Jinping was understanding of the US' grave concerns about advancements in North Korea's nuclear and ballistic missile programs.
But little more has happened since then and a senior White House official on Wednesday acknowledged that China's moves to ban North Korean coal imports was just a small step in the range of options China could consider to pressure the rogue regime in light of its trading relationship with North Korea.
"If Trump wants to get serious about applying greater pressure on North Korea, at this point that will require a more coercive attitude toward China," Ratner said.