ANKARA, Turkey — Since he started work as NATO secretary-general almost two years ago, Mark Rutte has spent much of his time trying to keep the United States anchored to the world’s biggest military alliance, employing outright flattery to dissuade U.S. President Donald Trump from acting on threats to abandon it.

But the goalposts keep shifting, raising the stakes ahead of this week’s summit in Turkey.

Initially, it was about money. Trump has long railed against NATO allies for spending too small a fraction of their national budgets on defense. But those problems were addressed at their summit last year, when U.S. allies committed to invest as much as America, in gross domestic product terms.

NATO’s real problem now is turning that money into military capabilities, particularly as European countries worry about a possible attack from Russia.

Still, Rutte tried to put to bed any lingering concerns at a White House meeting last month, with a new pitch using a chart labeled the “The Trump Trillion” in gold letters — showing $1.2 trillion in spending by European allies and Canada since 2017.

But Trump appeared unmoved, saying he was still disappointed at some NATO allies’ refusal to join the Iran war, which he had launched alongside Israel without consulting them.

“We don’t need their money — we don’t need anything,” Trump said. “I just want loyalty.”

Trump suggested he might have skipped the upcoming summit entirely were it not being hosted by Turkish President Recep Tayyip Erdogan. It’s a sign that even Erdogan and Rutte — foreign leaders Trump seems to hold in rare esteem — will have their work cut out for them in keeping the summit on track.

Historically, the prime tasks of NATO’s top civilian official — always a European, never an American — have been to encourage consensus in an organization that makes its decisions unanimously, and to speak on behalf of all 32 member countries.

But during both of Trump’s terms, Rutte and his predecessor at the helm of NATO, Jens Stoltenberg, have dedicated a huge amount of energy just to keep the United States inside their alliance.

Trump has threatened to leave NATO, dallied with pulling U.S. troops out of Europe and vowed to take over the island of Greenland — a semiautonomous part of ally Denmark. He has cast doubt over whether he would defend another member not spending enough on their military, eroding trust.

Rutte’s approach has been heavy on flattery. Last month’s carefully choreographed pitch in the Oval Office — with props redolent of an American flag — laid down a new marker, even for a man heavily criticized for likening Trump to a “daddy.”

The charts showed tens of thousands of U.S. jobs were being created and a backlog of $300 billion in European orders for military equipment — all thanks to the “leader of the free world,” Rutte said.

He pushed back, gently, on Trump’s complaints that NATO did not support the U.S. against Iran, noting that up to 5,000 U.S. planes took off from bases in Europe before an April ceasefire.

NATO cannot function without its biggest and most powerful ally. Europe is being pushed to fend for itself even as Russia, the historical reason for the alliance, poses a greater threat.

Last month, the Pentagon surprised its NATO allies by announcing that it was scaling back the number of troops, warships, aircraft and drones it would provide if one of them came under attack. Trump has also sent conflicting messages about whether U.S. troop numbers would be lowered or increased.

The cutbacks and mixed messaging has undermined unity at the alliance, just as Russia has been probing Europe’s defenses with drone flights near military bases across multiple countries, according to a study released on Thursday.

Each summit is meant to showcase the commitment to collective security — the all-for-one, one-for-all pledge enshrined in Article 5 of NATO’s treaty. It’s only been invoked once, when allies came to America’s aid after the Sept. 11 attacks.

The last NATO summit was held in The Hague, the hometown of Rutte, a former Dutch prime minister. The Dutch royal family hosted dinner, and Trump stayed overnight at the king’s palace.

Rutte got the allies behind a major defense spending pledge, and Trump left a happy man, calling his NATO partners a “nice group of people.”

This year, the summit will be hosted by Erdogan, another key NATO member with an independent streak. His close ties to Trump may keep the American president at the table, but it’s unlikely to mend the rifts.

Rutte has tried to convince Trump that his European partners are spending so much more that America can safely turn its attention to security challenges posed by China while they handle the war in Ukraine.

But Trump wants more now, and his demand for “loyalty” is hard to capture on any chart.

Rutte’s predecessor, Stoltenberg, has written in his memoir about chairing a 2018 summit that Trump nearly upended.

“If an American president says he no longer wishes to defend the other allies and leaves a NATO summit in protest, then the NATO treaty and its security guarantee aren’t worth very much,” Stoltenberg wrote.