The United States is to "re-engage" with the UN Human Rights Council, nearly three years after former president Donald Trump's administration withdrew.

President Joe Biden had instructed the US State Department "to re-engage immediately and robustly with the UN Human Rights Council", said new State Department chief Antony Blinken as the council met in Geneva.

Mr Biden's move marks another significant reversal of his predecessor's policies.

Mr Trump's administration took the country out of the 47-member council in June 2018.

He complained about its "unrelenting bias" against Israel and the "hypocrisy" of allowing rights-abusing nations a seat at the table.

The US departure left a void that China and others have been eager to fill at the council, created in 2006.

The United States cannot automatically regain membership, but has to wait for elections towards the end of the year.

Mr Blinken confirmed the US would initially be an observer at the council.

He stressed his country still regarded it as a "flawed body, in need of reform to its agenda, membership, and focus, including its disproportionate focus on Israel".

However the US withdrawal had done nothing to foster change, he noted. Instead, it had "created a vacuum of US leadership, which countries with authoritarian agendas have used to their advantage.

"To address the council's deficiencies and ensure it lives up to its mandate, the United States must be at the table using the full weight of our diplomatic leadership," he added.

Diplomats and rights groups welcomed the announcement.

Julian Braithwaite, the British ambassador to the UN in Geneva, stressing the importance of "full engagement" by all UN members in the council.

Jamil Dakwar, head of the American Civil Liberties Union's human rights programme, also hailed the new policy.

He cautioned that "the administration's credibility on international human rights will be judged by how close it will match its rhetoric with concrete actions to advance human rights at home and abroad."

Mr Dakwar called for the US to show "robust engagement to advance racial justice and dismantle systemic racism". 

The Council debated that issue last June, without US participation, following the death of George Floyd.

Mr Floyd's killing on 25 May 2020 after a white Minneapolis police officer - since charged with murder - pressed a knee on his neck for nearly nine minutes, set off a global outcry over racism and police brutality.

The Trump administration did not take part in the debate - but it was accused of pressuring participants to water down the final resolution to remove all specific mentions of the US.

During the council's Geneva meeting, US diplomat Mark Cassayre highlighted Mr Biden's rights-related initiatives since coming to office - on immigration, climate change, gender equality and gay rights.

And he emphasised Mr Biden's promise "to make strides to end systemic racism".

Mr Cassayre said the United States would commit to the "urgent" work of strengthening the council and defending human rights around the globe.  

"In the past few months alone, we have seen several emerging human rights challenges that deserve our immediate attention," he added. 

The rights council's next session will starts on 22 February through to 23 March. Due to the pandemic, most participation will be virtual.