VATICAN CITY -- Pope Francis cancelled a July trip to Africa due to ongoing knee problems. The Vatican announced Friday that the Vatican had received doctors' orders. This raises further questions about Pope Francis' mobility and health.

According to the Vatican, the July 2-7 trip in South Sudan and Congo would be rescheduled at a "later date to be determined."

"At the request of his physicians, and to not jeopardize his results of the treatment that he is undergoing to his knee, the Holy Father was forced to postpone with regret his Apostolic Journey in the Democratic Republic of Congo, and to South Sudan," said the Vatican in a statement.

Francis has been using a wheelchair for approximately a month because of strained ligaments in the right knee which have made it difficult to stand and walk.

However, plans for the trip to these two African countries were being made as of this week. The Vatican released the names and contact information of the accredited journalists who were to fly on the papal plane.

Questions have swirled over for months about Francis’ ability to navigate the trip, which would have been difficult for him even without his knee problems.

Francis has also planned a visit to Canada from July 24-30; the Vatican statement did not mention that trip and Matteo Bruni, spokesman for the Vatican, said that only the pope's other commitments had been confirmed.

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Alessandra Tarantino contributed.