Archbishop Carlo Maria Vigano, a senior Italian churchman who had called for Pope Francis to resign, said on Thursday he has been accused by the Vatican of schism and denying the pope's legitimacy.

Vigano, the papal envoy in Washington from 2011-2016, said he had been summoned to the Palace of the Holy Office at the Vatican on Thursday, either in person or via a canon lawyer. 

"I assume that the sentence has already been prepared, given that it is an extrajudicial process," he wrote on X, referring to a fast-track mechanism used by the Church.

Vigano, the papal envoy in Washington from 2011-2016, did not say whether he attended or was represented. 

The archbishop went into hiding in 2018 after conservative media published an 11-page statement in which he alleged the pope knew for years about sexual misconduct by an American cardinal and did nothing about it.

The Vatican has rejected the accusation of a cover-up of sexual misconduct. It was not immediately available for comment on Thursday.

Vigano said he was informed of the accusations against him by the Vatican's doctrinal office, the Dicastery for the Doctrine of the Faith.

"I regard the accusations against me as an honor," he added.

The Vatican document warned Vigano that he would be judged in his absence should he fail to appear, or to provide a written defence submitted by June 28.

Possible punishments could include removal from religious office or a bar on exercising the ministry.

"Archbishop Vigano has taken some attitudes and some actions for which he must answer," Cardinal Pietro Parolin, the Vatican's secretary of state, was quoted as saying in a report on the Vatican News website.

Italian media reported in the past that Vigano was upset because he was never made a cardinal by former Pope Benedict or because Francis blocked his further advancement in the Church.