The United States should push for the release of an Emirati activist "arbitrarily" detained in the UAE since 2017 ahead of this year's UN climate talks in Dubai, rights groups have urged.

Ahmed Mansoor was sentenced to 10 years in prison in 2018, accused of spreading false information on social media and harming the reputation of the state.

In a joint letter sent to US Secretary of State Antony Blinken on Wednesday, 19 groups including Human Rights Watch and Amnesty International called for diplomatic pressure on the United Arab Emirates to free Mansoor.

"We urge you to call on the UAE government to immediately and unconditionally release Ahmed Mansoor," the letter read.

They requested the US top diplomat "make this call publicly and to raise it in your engagement with UAE officials at the highest levels."

Rights groups have stepped up their lobbying for his release in the lead-up to the COP28 climate conference that will be held in the UAE business hub of Dubai from November to December.

"Washington should use this opportunity, when the UAE is trying to improve its image internationally in advance of the climate conference, to publicly and privately pressure Emirati authorities," Joey Shea, UAE researcher at HRW, said in a statement.

Mansoor, one of the most prominent rights activists in the UAE, received the prestigious Martin Ennals Award for Human Rights Defenders in 2015.

His arrest in March 2017 under the Gulf state's cyber-crime law triggered an international outcry and was heavily criticised by HRW and Amnesty.

In early August, the UAE said it would allow environmental activists to "assemble peacefully" at COP28, despite a prohibition on unauthorised protests in the Gulf state.

The oil-rich UAE requires official permission for protests but effectively bans demonstrations it deems disruptive.