BRUSSELS — Belgian Prime Minister Charles Michel scrambled to hold on to power Sunday, as his nation became the latest to face political upheaval caused by the planned adoption this week of a symbolic global pact on migration.

The controversy over the United Nations Global Compact for Safe, Orderly and Regular Migration revealed the degree to which the issue has become politically poisonous in the era of President Trump and rising far-right leaders in Europe. The nonbinding agreement, proposed by European leaders in the aftermath of the 2015 migration crisis in Europe, reaffirms existing commitments to human rights and seeks to broaden international cooperation to avoid future crises. But the United States, Israel, Australia and a lengthening tally of European countries say they will not sign on.

In Belgium, Michel’s decision to commit his country to the pact led the right-wing N-VA Flemish nationalist party to leave the ruling coalition late Saturday. The N-VA, which had held power over migration policy and sought to speed deportations from Belgium, declared that taking part in the pact meant giving up sovereignty over the country’s borders. Michel said he would pursue a minority government as he departed for the United Nations conference in Marrakesh, Morocco, where he will sign the document.

Migration is an issue “that cannot be solved alone,” he said Sunday.

The pact, which seeks to reduce the root causes of migration while making it safer for people who choose to move across borders, was the result of a European push to avoid repetitions of the drama of 2015. That year, more than a million people streamed into Europe, often by foot and under painful conditions. By signing the pact, countries pledge to respect the human rights of refugees and economic migrants, reduce the detention of migrants and offer them basic social services.

The effort has exposed just how controversial migration is, with a growing list of countries breaking away after the declaration was negotiated in July. 

In Germany, Chancellor Angela Merkel found herself fighting a rebellion not only from the far-right Alternative for Germany party but also from prominent members of her center-right Christian Democratic Party. At a parliamentary debate last month, Merkel said the pact would simply seek to ensure refugees and economic migrants are treated the same around the world as they are in Germany.

“It’s in our national interest that the conditions around the world, for refugees on the one hand and migrants on the other, are improved,” Merkel said.

The debate has roiled Poland, Hungary, the Netherlands, Italy, Slovakia and Latvia, among others. Even Austria, which was the lead negotiator of the pact on behalf of the European Union, has rebelled, with the ruling coalition declaring in October that it wanted to “defend its national sovereignty” instead of signing the agreement. Its defection set off a stream of new decisions to split from the pact.

The United States — which decided last year to sit out the negotiations — denounced the agreement Friday, saying in a statement from the U.S. Mission to the United Nations that “decisions about how to secure its borders, and whom to admit for legal residency or to grant citizenship, are among the most important sovereign decisions a State can make.”

Far-right campaigners have stoked the controversy. In Brussels on Saturday, former Trump campaign adviser Stephen K. Bannon appeared at a rally with far-right French politician Marine Le Pen, where both denounced the compact.

“At the heart of a country, at the heart of citizenship, is control of our borders and the citizens’ determination of that country on what its migration policies are going to be,” Bannon told the crowd.

Quentin Ariès contributed to this report.