United Nations (United States) (AFP) - A United Nations envoy on Tuesday took a swipe at countries dropping out of the UN migration pact, saying they were displaying "buyer's remorse" months after endorsing the non-binding deal.

The Global Compact for Safe, Orderly and Regular Migration was agreed at the United Nations in July following 18 months of negotiations and will be formally adopted at a conference in Marrakesh on December 10 and 11.

The United States quit negotiations early on, in December, and was followed by Hungary seven months later.

Since then, Australia, Israel, Poland, Slovakia, the Czech Republic, Austria, Switzerland and Bulgaria have either publicly disavowed the pact or notified the United Nations that they are withdrawing.

The pact promoting cooperation to deal with the world's growing migrant flows has been targeted by right-wing politicians who denounce it as an affront to their countries' national sovereignty.

"Some politicians, as it turned out, would say something like 'migration is a bad thing'," Louise Arbour, the UN special envoy for international migration, said.

"This is completely ridiculous. Migration is a thing. It's not a bad thing, not a good thing. It's a thing."

Arbour, a former Supreme Court of Canada judge and UN rights chief, said the countries exiting the compact were dealing with "buyer's remorse" after taking part in the lengthy negotiations and agreeing to the final text.

She suggested that countries quitting the UN's first-ever migration agreement would have to answer for their turnaround.

"It's going to be for the countries concerned to examine where it leaves them as international players," she said, "after having agreed, extracted concessions from others and agreed on a text."

- Who will go to Marrakesh? -

The global pact lays out 23 objectives to open up legal migration and better manage the influx as the number of people on the move worldwide has increased to 250 million, or just over three percent of the world's population.

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The deal had been held up as an example of a UN diplomatic success achieved without the United States at a time when President Donald Trump is questioning the relevance of the world body.

German Chancellor Angela Merkel is expected to be among the high-profile leaders at the Marrakesh conference next month, but it remains unclear how many other countries will be represented at a high level.

Israeli Ambassador Danny Danon told reporters that his country is not sending a representative to Marrakesh and linked the decision to pull out of the deal to upcoming elections.

"You have elections coming in a few months, so it's a very sensitive issue," he said.

After the Marrakesh conference, the General Assembly is set to adopt a resolution formally endorsing the migration deal.