The spiritual leader of the world’s 200 million Eastern Orthodox Christians was hospitalized Sunday in Washington on the first full day of a planned 12-day U.S. visit and will stay overnight, the Greek Orthodox Archdiocese of America said, writes ABCNEWS.

The archdiocese said Ecumenical Patriarch Bartholomew was preparing to leave for a service at the Cathedral of Saint Sophia in the nation"s capital when he felt unwell “due to the long flight and full schedule of events upon arrival”.

“His doctor advised him to rest and out an abundance of caution" go to George Washington University Hospital “for observation”, according to the archdiocese, Later Sunday, it said the patriarch “is feeling well” and was expected to be released Monday.

Bartholomew, 81, has a broad agenda spanning religious, political and environmental issues. His schedule includes a meeting Monday with President Joe Biden and various ceremonial and interfaith gatherings.

The patriarch is considered first among equals in the Eastern Orthodox hierarchy, which gives him prominence but not the power of a Catholic pope.