President Trump’s Twitter account is once again getting him into trouble, this time on North Korea. After decrying the Obama administration’s timidity with respect to Syria’s chemical weapons, the president now faces his own red line problem. Despite Trump tweeting in January that North Korea getting a nuclear-capable intercontinental ballistic missile “won’t happen” under his presidency, it looks like Kim Jong Un is getting close.

No one thinks that Kim Jong Un—who is proving a skillful tactician—is going to unilaterally disarm because of U.S. posturing. The only question is whether the Trump administration has the diplomatic dexterity to restart negotiations. The return to talks depends not only on how the president manages North Korea, but how he manages Beijing and some serious political constraints at home. Particularly in the wake of the death of Otto Warmbier, the University of Virginia undergraduate who recently died in North Korean detention, will engagement with the North Koreans look like capitulation?

The administration’s learning curve has been steep. The implicit deal coming out of the Mar-a-Lago summit between Presidents Trump and Xi Jinping of China was straightforward: The administration would delay pursuit of its protectionist economic agenda vis-à-vis China in return for help on North Korea. But Pyongyang continued to develop new missile capabilities—albeit delaying a sixth nuclear test so far—while Beijing remained cautious in how far it was willing to press.

China has the frustrating tendency to measure its willingness to help by discrete policy measures—a new sanction or statement—rather than by whether these measures have any material effect. President Trump’s frustration—“so much for China working with us”—is warranted. However, the problem he faces is deeper. In addition to their reticence, the Chinese have repeatedly stated that the purpose of pressure is not to bring North Korea to its knees, but to restart talks.

The current Chinese proposal for getting there starts with an unpalatable confidence-building measure that has come to be called “suspension-for-suspension.” North Korea would do little more than declare a moratorium on its nuclear and missile tests while the U.S. would suspend its annual military exercises with South Korea. Such a deal looks like straight extortion. But it is designed as a prelude to talks that would consider both American interests in denuclearization and North Korea’s proposal for a peace regime that would replace the Korean War armistice.

If talks don’t follow closely on the “suspension-for-suspension” trade, the U.S. will have paused military exercises for little more than a pause in Kim Jong Un’s march to a deliverable nuclear weapon.

The administration is thus searching around for leverage that would assure North Korea reconsiders its current course of action. Given limited military options, the administration has recently opted for secondary sanctions on Chinese entities doing business with North Korea, including a regional bank that is suspected of handling North Korean accounts. Such secondary sanctions would appear to make sense, and I support them. China has been enabling North Korea for long enough. By my calculations China does indeed account for about 90 percent of the country’s trade, although there is no evidence that bilateral trade has grown “40% in the first quarter” as another presidential tweet recently claimed. If the U.S. can bite into China-North Korea trade by dissuading larger Chinese firms from taking the risk of exposure to the country, then Kim Jong Un might well have miscalculated. Indeed, the country could be vulnerable to exactly the kind of foreign-exchange constraints that drove Iran to the bargaining table over its own nuclear program.

However, there is a catch. China strenuously opposes such measures and can easily dilute them by permitting other commercial trade and investment to proceed apace. Moreover, the administration has chosen the precise moment when it needs Beijing’s help to throw a succession of sharp elbows in China’s direction: a much-needed arms sale to Taiwan, signals that some trade enforcement actions are coming, and perhaps most concerning for the Chinese, a new freedom of navigation operation (FONOP in the lingo) in the contested South China Sea. Both the Taiwan and South China Sea actions might be warranted, yet are seen by China as touching on core sovereignty issues.

The administration claims to have done a review of its North Korea policy and landed on a formula it has labeled “maximum pressure and engagement.” The maximum pressure refers to the orchestration of more sanctions; the engagement, a stated willingness to resume talks. U.S. officials are on record as saying that the administration’s objective is to bring Kim Jong Un “to his senses, not to his knees.” This willingness to resume talks was reiterated during the recent summit with South Korean president Moon Jae In, at which the administration appeared to endorse Moon’s more engagement-oriented approach.

In the end, though, the problem cannot be outsourced to either China or South Korea. The G-20 summit this week provides an opportunity for Trump to do some diplomacy on the sidelines of the meeting. Yet key Asia strategy roles at State and Defense remain empty. In the absence of a strong North Korea team of his own choosing, it will be difficult for the president or his foreign policy team to manage the complicated negotiations with China on the parameters for nuclear talks. The administration also needs to sort out how to approach North Korea itself, if only to take Kim Jong Un’s temperature.

As with other foreign policy initiatives of the administration, this one is likely to end in embarrassing failure unless it engages the president’s attention. Such failure may not end in war, but will leave U.S. forces in the region seeking to deter a much more dangerous adversary. And as we are learning, the president’s attention is sorely limited to the length of a tweet.