By Anthony Deutsch

THE HAGUE (Reuters) -Dutch politician Mark Rutte, appointed to navigate NATO's tricky relationship with Donald Trump, looks set to nail his first summit as secretary general after securing a draft agreement on boosting European defense spending as the U.S. president wants.

Rutte has a name for negotiating political and financial minefields, and seemed unfazed last Friday when Spain at the last minute appeared to call into question its commitment to the spending goal of 5% of GDP that members are expected to accept in The Hague.

But even as tension over military budgets eased, new uncertainties arose as the U.S. bombing of Iranian nuclear sites loomed over Rutte's carefully stage-managed summit plans.

The 58-year-old is not only a tireless communicator and an analytical problem solver but also a prodigious builder of friendships, said Ron Fresen, who covered his record 13 years as Dutch prime minister for the public broadcaster NOS.

If the potentially awkward summit in Rutte's hometown of The Hague is a success, "it will largely be down to his political dexterity", said Fresen, author of the book "The Rutte Mystery".

Rutte announced his interest in the top NATO job in a local Den Haag FM radio interview with Fresen in 2023.

"He later told me he had made a mistake and hadn't intended to announce his candidacy," Fresen said, "to which I replied: 'You don't make mistakes like that'."

RUTTE'S COALITION-BUILDING SKILLS BROUGHT TO NATO

Rutte's first months at NATO have mostly been spent dealing with Trump rather than external adversaries, to the frustration of some members, said Sten Rynning, director of the Danish Institute of Advanced Study and author of "NATO: From Cold War to Ukraine, A History of the World’s Most Powerful Alliance".

The challenges have included Trump's threat to take Greenland from NATO ally Denmark, his suggestion that Canada become a U.S. state, his reduction in support for Ukraine and his scolding of its president, Volodymyr Zelenskiy, in the Oval Office.

Rutte has orchestrated the summit schedule to avoid further friction between Trump and European leaders over how to deal with Russia over its full-scale invasion of Ukraine since 2022.

"Most, let's say all, allies - except the United States - see Russia as a real threat and the driver of NATO defence. But not Trump. He sees it as an opportunity, and that gap has grown tremendously wide," Rynning said.

Instead of dealing with Russia, China and Iran, he said the summit had been set up to be a success "in the sense that they can announce that the alliance is united, that it is in agreement on defence spending".

Rutte is close to Zelenskiy and has unreservedly supported Ukraine. But he is walking a tightrope when it comes to NATO's role. Zelenskiy was not invited to the main event, avoiding a possible run-in with Trump, but only to a pre-summit dinner.

Yet disagreement over Russia, set aside for now, could ultimately become Rutte's greatest challenge, Rynning added.

For Rutte "this is not the time to cause it to fragment the alliance", he said, but in the long term "it is going to be his leadership challenge".

RIDING BICYCLE TO WORK AS PRIME MINISTER

For now, Rutte has merely sought to reassure Trump that Europe is ready to take on more responsibility for its own defence.

"This summit is about the Euro-Atlantic area, making sure that we can defend ourselves against the Russians -- the really fast-reconstituting Russians," he told reporters on Monday.

"That we are able to defend ourselves against China, which is also rapidly building up its capabilities, including 1,000 nuclear warheads by 2030. So we really need to spend more, produce more, keep Ukraine strong."

During four terms as prime minister, Rutte steered the Netherlands through the pandemic, forged coalition governments that bridged differences over asylum policy, mediated during the European debt crisis and took a tough stance against Putin after Russian-backed separatists killed nearly 200 Dutch nationals by shooting down an airliner over eastern Ukraine.

The former Unilever manager often arrived at government offices by bike, with an apple in hand, or in his unwashed Saab, living in a modest apartment in The Hague where he kept up weekly high school teaching while heading the cabinet.

Unmarried and with no children, he keeps both his private life and his emotions out of the media spotlight.

Generally well-humoured, he did once lose his cool with Fresen, who had sent a camera crew to cover a possible news event that turned out to be Rutte having a drink with friends.

"He called me in a rage and told me that if the footage was aired, he'd never talk to me again," Fresen said. But a few minutes later, Rutte called back to apologise.

(Reporting by Anthony Deutsch; Additional reporting by Stephanie van den Berg and Andrew Gray in The Hague; Editing by Kevin Liffey)