Russia and China are opposed to a candidate from Fiji seen as a staunch human rights defender to lead the top UN rights body, diplomats and observers say, creating a deadlock just as the United States may seek to rejoin the forum it quit in 2018.
The Human Rights Council presidency rotates annually between regions and is usually agreed by consensus, with any contests typically resolved quickly and cordially, diplomats say.
The impasse means the council, the only intergovernmental global body to promote and protect human rights worldwide, is set to resume work in Geneva next week with no leader for the first time in its 15-year history.
While its decisions are not legally binding, they carry political weight and can authorise probes into violations.
The infighting points to a high-stakes game where powers are seeking to pre-emptively counter future influence of the United States, which could rejoin the body under President-elect Joe Biden, Marc Limon of the Universal Rights Group think-tank said.
"Neither China nor Russia want a human rights-friendly country to hold the presidency in a year where the U.S. will probably re-engage with the council," he said.
Russia, China and Saudi Arabia -- sometimes acting through proxies -- have opposed the selection of Fiji's ambassador, Nazhat Shameem Khan, or thrown their weight behind other last-minute candidates, observers and two diplomats said.
"It's understood that Saudi Arabia, China and Russia were all supportive of a Bahraini candidacy and opposed to a Fijian candidacy," said Phil Lynch, director of the International Service for Human Rights, citing Fiji's record on rights in the Council where Khan, council vice president until December, backed probes into abuses in Belarus and Yemen last year.
The NGO is accredited to the council and takes part in debates.
The diplomatic missions for Fiji, Russia, China and Saudi Arabia did not immediately respond to requests for comment.
Khan has refused to step aside and alternative candidates from Bahrain and Uzbekistan put forward since December have not garnered a consensus, diplomats said.
Members have to be elected onto the 47-member Council to vote in its formal sessions. China and Russia, seen as more and more engaged in the body's work, both return to the Council this year after periods off it.
The president has limited powers although some say the role has become increasingly political in recent years, with Austria's ambassador Elisabeth Tichy-Fisslberger seen as exerting strong leadership last year.
The president appoints independent experts, such as the one in charge of extrajudicial executions who led an inquiry into the killing of Saudi journalist Jamal Khashoggi.
A review that could prompt reforms shaping the forum's future is due this year.
Attempts by Oman, last year's Asia-Pacific group coordinator, to resolve the matter via secret ballot hit Qatari opposition, creating a deadlock one diplomat called "a mess".
It is not clear how the impasse will be resolved. One option is a vote on Tuesday, but diplomats say China has opposed this as consultations continue.