(CNN) Besieged by a mounting clergy sexual abuse crisis, Pope Francis plans to meet on Thursday at the Vatican with Cardinal Daniel DiNardo, president of the US Conference of Catholic Bishops, and Cardinal Sean O'Malley, the pope's top adviser on clergy sex abuse.

DiNardo, of the archdiocese of Galveston-Houston, requested the meeting with Pope Francis as the Catholic Church in the United States faces clergy sex abuse scandals on several fronts. Spokespeople said DiNardo is not available for comment.

The Vatican confirmed the meeting, which will also include Archbishop Jose Gomez, vice president of the US Conference of Catholic Bishops, and Monsignor Brian Bransfield, the conference's general secretary. O'Malley is president of the Pontifical Commission for the Protection of Minors.

In an August 16 letter, DiNardo requested a meeting with the Pope following allegations that a former top American cardinal, Archbishop Theodore McCarrick, had sexually abused seminarians and an altar boy. McCarrick has denied the accusations about the altar boy and not responded to the allegations about the seminarians.

Those allegations, as well as an explosive letter from a formal papal diplomat, have raised serious questions among senior church leaders about why McCarrick was allowed to rise through the church's ranks, as well as who knew about the sordid accusations.

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