THE HAGUE, Netherlands >> NATO Secretary-General Mark Rutte praised President Donald Trump for making Europe “pay in a BIG way,” as leaders gathered Tuesday in the Netherlands for a historic summit that could unite them around a new defense spending pledge or widen divisions among the 32 member countries of the security alliance.

The U.S. president, while en route, published a screenshot of a private message from Rutte saying: “Donald, you have driven us to a really, really important moment for America and Europe and the world. You will achieve something NO American president in decades could get done.”

“Europe is going to pay in a BIG way, as they should, and it will be your win,” Rutte wrote. NATO confirmed that he sent the message.

Rutte appeared unconcerned that Trump aired it, telling reporters: “I have absolutely no trouble or problem with that because there’s nothing in it which had to stay secret.”

Trump arrived early in the evening and was driven to a dinner with other NATO leaders hosted by Dutch King Willem-Alexander at his palace in The Hague.

On Wednesday, the allies are likely to endorse a goal of spending 5% of their gross domestic product on their security, to be able to fulfil the alliance’s plans for defending against outside attack. Trump has said the U.S. should not have to.

Spain has said it cannot, and that the target is “unreasonable.” Slovakia said it reserves the right to decide how to reach the target by NATO’s new 2035 deadline.

“There’s a problem with Spain. Spain is not agreeing, which is very unfair to the rest of them, frankly,” Trump told reporters.

In 2018, a NATO summit during Trump’s first term unraveled due to a dispute over defense spending.

Ahead of the meeting, Britain, France and Germany committed to the 5% goal. The Netherlands is also on board. Nations closer to the borders of Ukraine, Russia and its ally Belarus had previously pledged to do so.

Trump’s first appearance at NATO since returning to the White House was supposed to center on how the U.S. secured the historic military spending pledge from others in the alliance — effectively bending it to its will.

But the spotlight has shifted to Trump’s decision to strike three nuclear enrichment facilities in Iran that the administration says eroded Tehran’s nuclear ambitions, as well as the president’s sudden announcement that Israel and Iran had reached a “complete and total ceasefire.”

Ukraine has also suffered as a result of that new conflict. It has created a need for weapons and ammunition that Kyiv desperately wants, and shifted the world’s attention. Past NATO summits have focused almost entirely on the war in Ukraine, now in its fourth year.

Still, Rutte insisted NATO could manage more than one conflict at a time.

“If we would not be able to deal with ... the Middle East, which is very big and commanding all the headlines, and Ukraine at the same time, we should not be in the business of politics and military at all,” he said.

Ukrainian President Volodymyr Zelenskyy arrived in The Hague for meetings, despite his absence from a leaders’ meeting aiming to seal the military spending agreement.

It’s a big change since the summit in Washington last year, when the alliance’s weighty communique included a vow to supply long-term security assistance to Ukraine, and a commitment to back the country “on its irreversible path” to NATO membership.

Zelenskyy’s first official engagement this time was with Dutch Prime Minister Dick Schoof at his official residence across the road from the summit venue.