Pope Francis today demoted an outspoken conservative American cardinal who has been highly critical of the pontiff's reformist leadership of the Roman Catholic Church.

Cardinal Raymond Burke, 66, was removed as head of the Vatican's highest court and appointed to the ceremonial post of chaplain of the charity group Knights of Malta.

The move, which the Vatican announced today without comment, had been expected. Cardinal Burke said last month he had been told he would move to a new job but did not know when.

Cardinal Burke, who until today was the highest-ranking American in the Vatican, gave a series of recent interviews criticising the pope and had emerged as the face of conservative opposition to Pope Francis' reform agenda.

In an interview with a Spanish magazine last month, Cardinal Burke, known for his unbending interpretation of doctrine, compared the Catholic Church under Pope Francis to "a ship without a rudder".

At a meeting of bishops from around the world last month, Cardinal Burke was the flag-bearer for conservatives opposed to the Church adopting a more welcoming attitude towards homosexuals.

Cardinal Burke has publicly clashed with the Pope several times since the Argentine pontiff's election in 2013 and Vatican sources have said the pope saw Burke's outspokenness as part of the so-called "culture wars" among Catholics that he wants to avoid.

During the synod, Cardinal Burke assailed German Cardinal Walter Kasper, who had argued that the Church should modify teachings that ban Catholics who have divorced and then remarried in civil services from receiving communion.

Cardinal Burke was also highly critical of an interim synod document that had talked more positively of homosexuals than ever before in Church history.

Shocked by the language, Cardinal Burke and other conservative bishops spearheaded a campaign that led to a much watered-down version in the gathering's final statement.

It was the second time in less than a year that the pope had sidelined Burke, the former archbishop of St Louis. Last December he removed Cardinal Burke from the board of the influential Vatican department that handles the appointment of bishops.

Cardinal Burke said last month he would be disappointed to leave his post at the top Vatican court, which oversees the administration of justice in the Church and hears appeals from lower Church tribunals, but would obey the Pope's orders.