The Donald Trump circus is in town. For the European leg of his first foreign tour, the scandal-ridden U.S. president will meet national leaders for a NATO meeting in Brussels before moving south for the G7 summit in Sicily. Having cheered on Brexit, dismissed NATO as "obsolete," and insulted Paris, Brussels and Sweden, he may not be expecting the warmest of welcomes.

But newspapers from Stockholm to Bucharest largely urged caution. It's never a good idea to slight the leader of the free world, commentators reminded their national leaders — especially one so erratic and impulsive. At a time when Europe depends on U.S. cooperation on countless issues — from Russian military aggression to international terrorism to climate change — the message was clear: Trump is not a man to trifle with.

99 problems but Europe ain't one

Trump’s tour comes after the mother of all bad weeks for his administration. And while some have said his visit to Europe might, ahem, "take the pressure off" his domestic woes, others were concerned he could end up in more hot water.

“Donald Trump could just have gone to Canada,” Michael Persson noted in Amsterdam daily De Volkskrant. But having chosen sensitive diplomatic terrain, Trump now has to navigate the “countless banana peels ready to slip up on” — from offending the Pope to upsetting NATO.

Still, there might be a silver lining. The trip could help Trump’s team get a handle on a media cycle that has spiraled out of control: “The speeches are written. The host countries will keep the press in check,” Persson noted. And it doesn’t matter if there is “a little bragging here, a historical blunder there" — any gaffes Trump might make "are in some ways already factored in.”

Europe’s commentators all stressed that NATO and G7 leaders would do better to bite their tongues.

Barcelona-based daily La Vanguardia was less convinced. In an editorial, the paper argued that Europe will be far less hospitable than Saudi Arabia, which spared no expense to flatter Trump’s ego. Given his “ability to insult allies as well as rivals,” the best one can hope for is that relations between Europe and the U.S. "will not have suffered any further setbacks" by the time he returns home.

For François Mathieu, joint editor-in-chief of Belgium’s Le Soir, the president's Brussels stint is likely to strengthen the “tornado” of scandals already swirling around him, saying he appears to unprepared for the tough meetings ahead. Far from helping him escape problems at home, Trump's European tour may (already) be his "last chance" to "recover some credibility." A mistake at any point could transform the Trump tornado into a cyclone.

Why so serious?

Despite Trump’s domestic political disasters and, to put it mildly, his unconventional leadership style, Europe’s commentators all stressed that NATO and G7 leaders would do better to bite their tongues, repress thoughts of the Access Hollywood tape, and take the new president seriously.

After months of heightened tension between Sweden and Russia, it is perhaps not surprising that Swedish papers were among the loudest voices to call for a stronger transatlantic relationship.“If Sweden wants to ensure American support in a conflict situation, the government must show that we mean serious business," Stockholm-based daily Expressen warned. This involves assuring the Trump administration that Sweden is prepared to “take responsibility for our own security” by raising military spending to 2 percent of GDP.

European leaders should seize on Trump's apparent warming toward the alliance he had disparaged on the campaign trail to have a "serious discussion about the future" when NATO members meet in Brussels, Dutch Socialist MP Bastiaan van Apeldoorn wrote in Trouw. But they will also have to be on guard against efforts by Trump — who is expected to insist that NATO formally joins the coalition against ISIS — to send it down the wrong path.

Trump may love provocation, Hans van Soest wrote in Rotterdam’s Algemeen Dagblad, but Europeans should focus on the "seriousness" of the occasion. Trump may behave much more erratically than his predecessors, but his underlying demands remain the same. He “is not the first president to call on us to abide by our [military spending] commitments — Obama did it as well," Soest reminded readers.

Dumitru Constantin, a columnist for Bucharest daily Cotidianul, agreed. While American presidents' first foreign trip have a powerful symbolic importance, Trump’s presence at the NATO summit “is in fact purely routine," he argued.

Others dwelled on the irony of Trump's pledge to tackle the threat of international terrorism by teaming up with Saudi Arabia — "an important sponsor of terrorist movements" in Europe, according to Jan Jandourek, a columnist for Prague-based online daily Forum24. Jandourek suggested the U.S. president read European newspapers more carefully. If he did, “he would discover that Saudi Arabia, Kuwait and Qatar provide support for extremist Islamic groups in Germany.”

Le Monde Washington correspondent Gilles Paris was one of the few commentators to discuss the impact of Trump’s visit on the future of the planet. Keeping the U.S. in the Paris Agreement will be a key goal of the G7 summit, especially as far as newly elected French President Emmanuel Macron is concerned. The task will be made harder, however, by Trump’s fuzzy attitude to multilateralism: “He has often implied that it is an affront to U.S. sovereignty without exactly formulating a well-defined doctrine.”

Keep calm and carry on

Above all, commentators warned European leaders against provoking the notoriously thin-skinned president.

The visit would have been fraught even under the best conditions, as Hubert Wetzel wrote for Die Süddeutsche Zeitung from Washington. But times are "not normal" and Trump is "not traveling the world as a strong, politically secure U.S. president.” His European partners have little to gain from "making the president’s life even harder,” Wetzel argued. It would be foolish “to anger Trump by not greeting him with full respect — regardless of whether they see him as a particularly competent colleague.”

David Usborne, U.S. editor of the Independent, took a similar tone: “Even those who will be naturally inclined to disdain Trump and the populist instincts that carried him to the White House [...] will know to keep their feelings in check, and not just because he is a man who holds grudges and seeks revenge when he senses disrespect.”

Nevertheless, Trump can expect a cool reception in Brussels and in Sicily, where “the other G7 leaders will poke him over free trade and his threat to take the United States out of the Paris climate accord,” Usborne predicted.

In any case, Europe's best conciliatory efforts may not be enough. Trump “will not be content with nice words,” La Stampa columnist Stefano Stefanini warned. The U.S. president “operates on a transactional basis” and can’t return home empty-handed.

If Europe wants to win concessions on major issues like international trade and immigration, it will need to do more than simply avoid ruffling his feathers.

Simon Pickstone is the English language editor of VoxEurop, a news and debates platform that covers European issues in 10 languages.