BRASILIA - Brazil's Supreme Court (STF) began an extraordinary session Thursdasy to rule on whether the impeachment vote against President Dilma Rousseff, scheduled for Sunday in the Chamber of Deputies, should be scrapped due to process irregularities.

The session was called after the country's attorney-general's office (AGU) presented a formal request to cancel the process.

The AGU filed the request at noon Thursday, asking the STF to stop Chamber of Deputies President Eduardo Cunha from holding an official vote to rule on whether Rousseff should be impeached.

In the document, the AGU said that there had been "irregularities to due legal process and the right to a defence" during the analysis of the charges against Rousseff by a special congressional commission, which ruled Monday it was in favor of the impeachment vote going ahead.

It added that this impeachment process presents "an immediate risk to the rights of the president, to the public interest and ... to Brazilian democracy itself".

The STF, the document said, should also consider whether the facts warrant the impeachment of Rousseff.

Various members of the government's ruling bloc have also requested that the STF provide clarification on the impeachment proceedings.

The STF, however, said Thursday that its extraordinary session will not consider the validity of the accusations against Rousseff and only consider whether any irregularities in the process meant the vote should be canceled.