RIO DE JANEIRO, May 9 (Xinhua) -- Brazil's Senate leader Renan Calheiros said on Monday the Senate will vote as scheduled on a motion to open an impeachment trial against President Dilma Rousseff, despite a sudden lower house about-face.

The lower house reversal, announced just two days before the Senate is to vote on Wednesday, "is an untimely decision," said Calheiros, and as such "cannot be accepted."

Accepting the lower house's decision to nullify its April 17 vote in favor of the impeachment drive would only serve to "delay the process," said Calheiros.

"It is not up to the president of the Senate to say whether the process is just or unjust, it is the decision of the plenary, of all of the senators," he added.

The lower house vote in April paved the way for the impeachment case to reach the Senate, but earlier on Monday Brazil's newly-instated interim lower house speaker Waldir Maranhao announced his decision to nullify that vote.

Maranhao's last-minute acceptance of an injunction filed last week by Brazil's Attorney General Jose Eduardo Cardozo, citing irregularities in the voting process, disrupted the impeachment drive that has otherwise been moving ahead briskly.