Buddhism has been Mongolia's dominant religion for centuries, and the country's last king, Bogd Khan, was born in the Tibetan capital of Lhasa.

The Gandantegchinlen Monastery has long been the heart of the faith in Mongolia, where more than half the population identifies as Buddhist.

The Dalai Lama insisted this week that his office "exclusively" would name his successor, even as China said it would do so.

Worshipper Jamyandorj Baljinnyam credited him with bringing about a renaissance in the faith.

"Before the Dalai Lama, Buddhism wasn't well known in many parts of the world," he told AFP.

"Thanks to his influence, everyone now accepts that Buddhism is not only a religion but also a comprehensive scientific philosophy," he said.

"He brought us all together. I even know worshippers from Africa."

China's government insisted this week that the next Dalai Lama must be appointed with its approval, in a process carried out by drawing lots from a golden urn under a method introduced by a Qing dynasty emperor in the 18th century.

That urn is held by Beijing and the Dalai Lama has already warned that, when used dishonestly, it lacks "any spiritual quality".

Buddhist institutions wield significant political influence in Mongolia, which is sandwiched between Russia and China, and many there were reluctant to speak openly about the succession given its sensitivities.

Ruth Gamble, a historian of Tibet at Australia's La Trobe University, said Mongolian Buddhists could find themselves trapped in a geopolitical clash with a uniquely spiritual bent.

"I think we're going to end up with two Dalai Lamas, or two people understood by different groups to be Dalai Lamas," she told AFP.

"Who will the other Buddhist, Tibetan Buddhist, or Vajrayana Buddhist countries like Bhutan and Mongolia -- which side of this debate will they go on?"

In the Gandantegchinlen Monastery, where visitors spin golden Tibetan prayer wheels on which mantras are written, worshipper Baasanbat Ulzii said she prayed to the Dalai Lama's portrait every night.

"It makes everything feel complete," she told AFP.

"He's turning 90 years old, which is such a long time," she added.

"I truly hope the next Dalai Lama continues his legacy, uniting all Buddhist communities under one roof and spreading goodness through his will."