Can António Guterres scare Donald Trump into taking the United Nations seriously?

Since taking office in January, the U.N. secretary-general has done his level best to build a decent working relationship with the new administration. He has kept criticisms of the White House’s nationalist agenda to a bare minimum. While pleading with Washington to refrain from deep cuts to the U.N. budget, he has worked assiduously to build a rapport with U.S. Ambassador Nikki Haley. Testifying in Congress on Tuesday, Haley noted that Guterres had agreed that the U.S. could safely make some cuts to its funding of blue-helmet peace operations — a message likely to rile up other U.N. members who may have to make up the difference.

But there are limits to even the most discreet international civil servant’s patience. Over the past month, Guterres has been trying out a new message: Trump is handing the world to China.

The secretary-general, who is also visiting Washington this week for consultations on Capitol Hill, tried out this line for the first time in late May. Speaking on the eve of President Trump’s decision to withdraw from the Paris climate change agreement, he warned that if the U.S. created a “geostrategic vacuum” by giving up its global role, “I guarantee that someone else will occupy it.” He clearly implied this would be Beijing.

Guterres, who was once a professional physicist, summoned up the vacuum metaphor in a midyear news conference last week, but with more of a pro-American twist. “I don’t think this is good for the United States,” he said of other powers’ potential power grab, “and I don’t think this is good for the world.”

Many pundits have highlighted how China is benefiting from Trump’s foreign policy mess in far starker terms. But it is striking that a secretary-general is talking even this frankly about geostrategic power shifts. Whatever the U.N.’s conservative foes say about the organization, international officials hate criticizing America in public. The U.S. remains the organization’s predominant funder. Washington has been brutal with previous secretaries-general who have criticized its policies, as Kofi Annan did over Iraq.

A former Portuguese prime minister with decades of experience in top-level political wheeling and dealing, the secretary-general prefers to work quietly behind closed doors

So Guterres will not have played the China card lightly. He is not the sort of politician who picks unnecessary fights. A former Portuguese prime minister with decades of experience in top-level political wheeling and dealing, the secretary-general prefers to work quietly behind closed doors. He is comfortable with making hard-nosed diplomatic compromises. To secure Moscow’s support for his campaign to run the U.N. last year, for instance, he promised to put a Russian in charge of U.N. counterterrorism efforts.

Guterres initially appeared to hope that he could win over the Trump administration through similar means. He has invested heavily in developing personal ties with Haley, Trump’s very un-Trump-like ambassador. In March, Guterres effectively forced out a U.N. development official who released a report accusing Israel of “apartheid” policies, and Haley publicly applauded his stance. His team has searched hard for ways to cut the organization’s costs, such as trimming peacekeeping operations, which allows Haley to tell Washington that she is forcing the U.N. to shape up. He even visited the former governor’s home state of South Carolina to give a university commencement address and meet local politicians to signal his alliance with the ambassador.

In many ways, Guterres is the perfect secretary-general from a U.S. point of view. His predecessor, Ban Ki-moon of South Korea, could be almost slavishly loyal to Washington, undermining his credibility with other countries. Guterres has a much broader political base, with strong personal links to leaders in Africa and Latin America as well as Europe. He was once the president of the Socialist International, which makes it pretty hard to portray him as Republican stooge. But his preference for backroom diplomacy and acute sense of the need to keep the U.N.’s biggest powers happy mean that he avoids open spats with the U.S. whenever possible.

But even a wily diplomat like Guterres could not duck fighting the administration indefinitely — Trump’s aggressive attitude to the U.N. in general, and the Paris deal in particular, guarantees that. As he must now be aware, even a solid working relationship with Haley cannot protect him and the U.N. from the president’s whims and outbursts. Guterres has also been looking for allies elsewhere to back up the U.N. if his efforts to keep the U.S. engaged fail. He met Emmanuel Macron within days of the French president’s election, and has devoted time to consolidating relations with the U.N.’s traditional supporters in the European Union.

The secretary-general’s most significant relationship outside the U.S., however, will ultimately be with China. Following Trump’s election, there has been a wave of Sinophilia in and around the U.N., with international officials murmuring that it is time for Beijing to take on a greater leadership role. In reality, China only seems interested in bolstering those parts of the U.N. system that directly serve its interests.

If Guterres draws closer China, Trump will doubtless claim that this proves the U.N. has had an anti-American agenda all along

Chinese officials have been firm in defense of the Paris agreement, which President Xi Jinping helped engineer with the Obama administration, but remain sniffy about such Western creations as human rights monitoring. Nonetheless, Guterres has made a notable effort to court China, visiting Beijing in May for a conference on its “One Belt, One Road” trade initiative and praising its “win-win” development initiatives.

This does not mean that Guterres is actively planning to facilitate a Chinese takeover of the U.N. For now, he is largely hinting at the possibility of Beijing filling America’s geostrategic vacuum in an attempt to coax the U.S. back into line. He is unlikely to get much of a hearing from Trump — the two have met only once in person—but he has some access to more mainstream Republican figures in Congress through Haley. By talking obliquely about the future of U.S. power, the secretary-general is signaling that he grasps Washington’s geopolitical concerns, and is not just a well-meaning humanitarian.

In the short term, Guterres will hope that he can persuade Congress to roll back some of the vicious cuts to American funding the U.N. laid out in the administration’s 2018 budget. Yet unless Trump eases off the U.N. over the longer term, the secretary-general may find that he has to follow through on the logic of his recent warnings and make more concrete overtures to Beijing. At a time when wars and humanitarian crises are piling up on the U.N. — the organization says it needs $8 billion to deal with the fallout from the conflict in South Sudan alone — Guterres cannot keep playing footsie with the U.S. indefinitely. He will need to turn to those powers that are willing to offer serious quantities of financial and political aid, and if China is willing to increase its assistance, the U.N. will simply have to follow the money.

If Guterres draws closer China, Trump will doubtless claim that this proves the U.N. has had an anti-American agenda all along. But the administration should listen carefully to what the secretary-general is saying. He wants to keep U.S. power alive at the U.N. But if that proves impossible, he has to have a Plan B for Beijing.