Pope Francis is on his way to Quebec for meetings on Wednesday with Canada's political leadership, a largely diplomatic pause from the main purpose of his trip - apologizing for the Church's role in running indigenous schools.

Francis left Edmonton, Alberta, for Quebec's capital city, where he is due to arrive mid-afternoon. Due to the delay of a second plane carrying indigenous leaders and trip organizers, the pope's schedule has been pushed back by an hour, the Vatican said.

The pontiff will hold his meetings at the Citadelle de Quebec, the largest British fortress built in North America.

The Citadelle, which sits on the banks of the St Lawrence River, is a historic site and one of the official residences of Canada's governor general, Mary Simon, who is the representative of Queen Elizabeth, the head of state.

Francis will start with a meeting with Simon, who is the first indigenous person to serve as governor general. He then holds an official meeting with Prime Minister Justin Trudeau, who has made reconciliation with Canada's indigenous peoples one of his political priorities.

Francis will speak to about 100 officials, diplomats and indigenous leaders after the official meetings.

On Tuesday, the pope presided over an open-air Mass in a football stadium while seated because of a knee ailment. Later, he visited Lac Ste. Anne, a pilgrimage site popular with both indigenous Canadian Catholics and those of European origin.

There, he said the Roman Catholic Church should accept institutional blame for the harm done to indigenous Canadians in residential schools that tried to wipe out native cultures. [L1N2Z71BZ]

During his first full day in Canada on Monday, the pope traveled to the town of Maskwacis, site of two former schools, and issued a historic apology that called the Church's role in the schools, and the forced cultural assimilation they attempted, a "deplorable evil" and "disastrous error".

More than 150,000 indigenous children were separated from their families and brought to residential schools over the years. Many were starved or beaten for speaking their native languages and sexually abused in a system that Canada's Truth and Reconciliation Commission called "cultural genocide".

On Thursday, Francis will visit the Sanctuary of Sainte-Anne-de-Beaupre, the oldest Catholic pilgrimage site in North America, and meet the archbishop of Quebec, Canada's largely French-speaking province, in the Notre-Dame de Quebec Cathedral.

On his way back to Rome on Friday, he will stop for a few hours in Iqaluit in the Canadian Arctic, where indigenous issues will return to the fore.

(Writing by Steve Scherer, additional reporting by Anna Mehler Paperny; Editing by Robert Birsel and Deepa Babington)