She cited the admission of the Democratic Republic of Congo as a member state after mass graves were discovered in the country and the council's failure to address human rights abuses by Venezuela and Iran while regularly passing resolutions condemning Israel.
She said the decision was an affirmation of USA respect for human rights, a commitment that "does not allow us to remain a part of a hypocritical and self-serving organisation that makes a mockery of human rights".
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"We thank the Secretary General for recognizing that the United Nations must reform if it is to be an effective partner in confronting threats to sovereignty, security, and prosperity".
The 47-member council has a number of powers, including the ability to establish panels that probe alleged human rights abuses.
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Human Rights Watch said in a statement the U.S. government's decision will sideline the country from key global initiatives to protect human rights.
The announcement would come just one day after the UNHRC condemned the Trump administration for its policy of separating children from the familes at the US-Mexico border.
Leaving the council would would be the latest rejection by the USA of multilateral efforts, including the Paris climate agreement and the Iran nuclear deal.
Mexican Foreign Minister Luis Videgaray Caso said the separation of children from parents at the USA border was "cruel and inhuman", and clearly violated human rights. UN High Commissioner for Human Rights Zeid Ra'ad al-Hussein on Monday called on Washington to halt its "unconscionable" policy.
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But the special counsel is a Republican and some others on his team owe their jobs largely to Republican presidents. Trump added that he feels "badly for some people, because they've gone back 12 years to find things about somebody.
Human Rights Watch criticised the move, warning that Washington's absence at the top United Nations body would put the onus on other governments to address the world's most serious rights problems.
Israel is the only country in the world whose rights record comes up for discussion at every council session, under "Item 7" on the agenda.
"Today we need to be honest". Nonetheless, he said the United Kingdom wasn't "blind to the value of this council". It also wanted more strict guidelines for membership, as well as the ability to kick out countries with a record of human rights violations.
"The US's absence will only compound the council's weaknesses", they wrote. No other country has such a mandate leveled against it.
What is the UN Human Rights Council?
Situations in Syria, North Korea, Myanmar and South Sudan are among the investigations launched by the council.
This is the first time a member of the council would leave the body voluntarily.
Barack Obama made a decision to have the United States rejoin the new UNHRC shortly after taking office. US's term was to end next year.
"Reform necessary, but United Kingdom is here to stay - UN Human Rights crucial to holding states to account", he said in a brief message via Twitter.