Bishop Blase Cupich, Pope Francis' first major appointment in the hierarchy of the US Catholic Church, will knock at the door of Chicago's Holy Name Cathedral on Monday evening as part of the ritual beginning his term as the city's new archbishop.

Cupich, 65, the Spokane, Washington, bishop who is seen as a moderate, succeeds the more conservative Cardinal Francis George, 77, who is retiring. Cupich's installation Mass will be held on Tuesday afternoon.

Chicago, with more than 2.2 million parishioners, is the third-largest US diocese by population and its archbishop has traditionally played a major role in the American Church hierarchy and in relations with local and national political leaders.

The city's archbishops are typically elevated to the rank of cardinal, meaning Cupich would be able to enter a conclave to elect a pope after Francis's death or resignation.

Cupich will be greeted at the cathedral door on Monday night by George and other religious leaders. The ceremony will include a sermon by Cupich, known as the homily.

Todd Williamson, director of the archdiocese's Office for Divine Worship, said the knocking ritual is a centuries-old liturgical gesture and means exactly what it seems to mean.

"He's the new archbishop and is knocking, wishing to enter his cathedral," Williamson said, adding that it used to be done with the bishop's crosier, or staff.

A native of Omaha, Nebraska, Cupich studied at Catholic universities in the United States and the Pontifical Gregorian University in Rome.

Crux, a major US Catholic website associated with the Boston Globe, said Cupich is "widely viewed as a moderate voice among Catholic bishops [and he] often eschews cultural battles in favor of dialogue and engagement."

Cupich's views are seen as in line with Francis' call for compassion rather than condemnation or confrontation on issues such as abortion and same-sex couples.

Francis also has called on bishops not to live like princes, and Cupich has said he will live in modest quarters at the cathedral rectory, rather than in the 19-chimney mansion on Chicago's Gold Coast which has been home to the city's archbishops since 1885.

George is undergoing treatment for cancer and has said he needs to focus on his health.