Boris Johnson has described the United States' decision to withdraw from the UN Human Rights Council as "regrettable" - and says the UK is "here to stay".
Donald Trump's envoy to the United Nations announced the news of America's withdrawal on Tuesday, calling it "an organisation that is not worthy of its name".
Nikki Haley said she had made it clear a year ago that the US would only stay in the council if "essential reforms were achieved" - and said those calls had not been heeded.
In response to the news, Mr Johnson admitted the world body was in need of reform, but stressed that Britain's support for it remained "steadfast".
He said: "The United States' decision to withdraw from the Human Rights Council is regrettable.
"We've made no secret of the fact that the UK wants to see reform of the Human Rights Council, but we are committed to working to strengthen the council from within."
The Foreign Secretary said the UK would "continue to support and champion it", adding: "It is the best tool the international community has to address impunity in an imperfect world and to advance many of our international goals."
On Twitter, he said: "US decision to withdraw from the Human Rights Council is regrettable. Reform necessary, but UK is here to stay - @UNHumanRights crucial to holding states to account."
Ms Haley announced the US withdrawal at the State Department alongside US secretary of state Mike Pompeo.
She said the council had been given "opportunity after opportunity" to make changes, and accused it of having a "chronic bias against Israel".
She also decried the membership of countries such as China, Cuba and Venezuela that are themselves accused of rights violations, and said the body was a "hypocritical and self-serving organisation that makes a mockery of human rights".
Ms Haley added that the US would be willing to rejoin if the organisation does reform.
The UN Human Rights Council was created in 2006 and aims to protect human rights around the world. The US joined in 2009 under Barack Obama.