Pope Francis has voiced his happiness to visit Buddhist-majority Mongolia from Friday where Catholics make up for their small numbers with "vibrant faith".

The "much-desired visit" offers a chance "to embrace a Church small in numbers but vibrant in faith and great in charity," Francis said at Sunday's Angelus prayer on Saint Peter's Square.

He said he looked forward to meeting "a noble, wise people with a great religious tradition" in the vast Asian nation nestled between China and Russia.

The pope is due to meet political authorities, address Church representatives and join an inter-religious gathering before celebrating mass in a sports arena.

The Catholic community of Mongolia -- a former Soviet satellite which adopted a multi-party system in 1992 -- is one of the smallest in the world with an estimated 1,450 faithful out of a population of more than three million.

The pope thanked the Mongol authorities for "their courteous invitation" along with "those who are preparing my visit with such enthusiasm".

The five-day visit, which includes a nine-hour flight from Rome to Ulaanbaatar, will also test the 86-year-old's health after a hernia operation in June and difficulties walking.

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