LONDON — President Donald Trump’s candidate to lead the U.N.'s migration agency was rejected by delegates on Friday — only the second time since the organization's founding in 1951 that it won't be run by an American.

The candidate, Ken Isaacs, had reportedly made or re-posted a number of disparaging remarks about Muslims on social media while serving as vice president of the Christian charity Samaritan’s Purse.

After Isaacs was rejected, delegates in a secret ballot chose António Vitorino of Portugal as director general of the International Organization for Migration (IOM).

The decision to reject Isaacs comes at a crucial moment for migration issues worldwide, and at a time when the Trump administration has been increasingly critical of international institutions. The U.S. pulled out of the U.N.'s Human Rights Council this month, and Trump has criticized the World Trade Organization as "unfair" to the U.S.

BREAKING: António Manuel de Carvalho Ferreira Vitorino elected as new Director General of IOM. pic.twitter.com/PNi72ItYWR — IOM - UN Migration (@UNmigration) June 29, 2018

According to the IOM's mission, the 169-member Geneva-based agency promotes the “orderly and humane management of migration” and “international cooperation on migration issues,” as well as encourages practical solutions to migration problems, and provides humanitarian assistance.

The director general has traditionally been filled by an American, with delegates accepting the United States’ chosen candidate. The last time a non-American led the organization was in the 1960s.

However, since the IOM became affiliated with the United Nations in 2016, there had been speculation that the change in status would cause governments to challenge that assumption.

Keith Michael Harper, the Obama administration's ambassador to the U.N. Human Rights Council, tweeted that Friday’s ballot was a sign that U.S. authority has been “dramatically diminished” on the world stage.

Yet another sign that US power, authority and prestige has been so dramatically diminished. IOM Director is seen as an “American seat” and Trump was unable to place an American in it. https://t.co/uSxDcTfgnU — Keith Michael Harper (@AmbHarper) June 29, 2018

Isaacs' candidacy was blighted by reports of his comments on Islam, including a Washington Post article in February that said he had re-posted and made an anti-Muslim comment on a CNN story about a June 2017 terrorist attack in London.

The story quoted a Catholic bishop as saying: “This isn’t in the name of God, this isn’t what the Muslim faith asks people to do.”

According to the Post, Isaacs then commented: “CNN, Bishop, if you read the Quran you will know ‘this’ is exactly what the Muslim faith instructs the faithful to do.”

Then in March, CNN reported that Isaac’s private Twitter account had retweeted posts from anti-Muslim figures alleging creeping Sharia law in the United States, and that Islam was trying to destroy the country from within.

However, Mark Hetfield, a friend of Isaacs who heads the humanitarian group HIAS, which works with IOM, put the blame on the policies and rhetoric of Trump himself rather than Isaacs.

"This IOM election really was not about Ken Isaacs, for whom I have a lot of respect as a humanitarian," Hetfield said.

"The election was an international referendum rejecting President Trump and his xenophobic, Islamophobic and isolationist policies," he said. "Let's face it, Isaacs' tweets were no worse than the ones coming out of the White House."

Isaacs did not respond to a request for comment.

Vitorino will succeed William Lacy Swing — a former U.S. ambassador who served 10 years as IOM director general — on Oct. 1, the organization said in a statement.