Rome — Finished at last with their three-month job of forming a government, Italy’s populists on Friday recited oaths, shook hands and began a job that could prove even more challenging: running the euro zone’s third-largest economy while risking a deep conflict with the European Union.

Italy’s new government has signaled it doesn’t intend to leave Europe’s single currency, easing the most acute concerns. But even with that threat averted for now, Italy’s populist coalition, in a bid to fulfill campaign promises, could test Europe on issues including migration and spending.

For a continent already strained by Britain’s exit from the EU and an increasingly uncertain relationship with the United States, Italy represents a different kind of peril. It is a core European Union member willing to push back against European Union policies and norms. In a note of congratulations on Friday, European Council President Donald Tusk said it was a “crucial time” for Italy and the EU.

“We need unity and solidarity more than ever,” Tusk said.

Italy’s populists, so far, have offered Europe conflicting signs about the approach they will take. The dramatic deal to form a government — and win sign-off from President Sergio Mattarella — was only clinched when the leaders swapped out a fierce euro critic for the finance minister job. Italy’s new government also chose as foreign minister Enzo Moavero Milanesi, whom one analyst on Friday called “a piece of the Italian-European establishment if ever there was one.”

But the two parties that overturned Italy’s political power structure also have reason to stick with the anti-Europe message, because that is what helped bring them to power. The anti-establishment Five Star Movement and the hard-right League have talked relentlessly about renegotiating European rules and fiscal limits. They have called on Europe to help find a more equitable solution for settling migrants and ease the burden on Italy, a top entry point for immigrants crossing the Mediterranean. The League, in particular, has taken a strident anti-migrant stance, campaigning on the deportation of 600,000 people.

“These guys were supposed to overturn the world,” said Giovanni Orsina, a professor at the LUISS Guido Carli University in Rome, who said he already sees some indications of normalization. “They promised the moon and now they get to govern. They will need to show voters they are moving.”

Much of the concern about Italy’s new government stems from its promise of a powerful injection of spending, including new subsidies for the poor and unemployed. The coalition wants to repeal an unpopular pension restructuring that was drawn up during the height of the euro crisis as a way to bolster Italy’s coffers.

The proposed changes are a potent nod to voter frustration in a country where the economy has scarcely grown in two decades.