The United States has withdrawn from the UN Human Rights Council, US ambassador Nikki Haley said Tuesday, branding the global body a "cesspool of political bias."
"We take this step because our commitment does not allow us to remain a part of a hypocritical and self-serving organization that makes a mockery of human rights," she said.
Haley has repeatedly threatened to quit the Geneva-based body, established in 2006 to promote and protect human rights worldwide.
UN spokesman Stephane Dujarric declined to comment ahead of the announcement, saying: "We will wait to hear the details of that decision before commenting fully."
"What is clear, is that the secretary-general is a strong believer in the human rights architecture of the UN and the active participation of all member states in that architecture."
UN officials privately confirmed they were expecting the US decision to quit the rights body.
The withdrawal followed strong UN criticism of Trump's policy to separate migrant children from their families at the US-Mexico border.
UN rights chief Zeid Ra'ad Al Hussein said Monday "the thought that any state would seek to deter parents by inflicting such abuse on children is unconscionable."
Human Rights Watch criticized the move, warning that Washington's absence at the top UN body would put the onus on other governments to address the world's most serious rights problems.
"The Trump administration's withdrawal is a sad reflection of its one-dimensional human rights policy: defending Israeli abuses from criticism takes precedence above all else," said HRW's executive director Kenneth Roth.
"The UN Human Rights Council has played an important role in such countries as North Korea, Syria, Myanmar and South Sudan, but all Trump seems to care about is defending Israel."
US criticism stems from the fact that Israel is the only country that has a dedicated agenda item, known as Item 7, at the rights council, meaning its treatment of the Palestinians comes under scrutiny at each of the body's three annual sessions.
The United Stated refused to join the body when it was created in 2006, when George W. Bush was in the White House and his ambassador to the UN was John Bolton, Trump's current hawkish and UN-skeptic national security advisor.
It was only after Barack Obama came to power that Washington joined the council in 2009.
Since Trump took office, the United States has quit the UN cultural agency UNESCO, cut UN funding and announced plans to quit the UN-backed Paris climate agreement.