Brazilian President Dilma Rousseff said Monday she was surprised by the decision of the interim head of the country's House of Deputies to overturn last month's vote by the lower chamber to impeach her.
Waldir Maranhao cited procedural mistakes in making his decision to annul the April 17 vote and call for a new vote.
Rousseff said on Twitter that she had not officially received the information and did not know the consequences of Maranhao's decision.
Opposition parliamentarians said they would go to the Supreme Court to block Maranhao's decision, news portal G1 reported. Pauderney Avelino, a deputy in the lower chamber, said the impeachment is now before the Senate and therefore cannot be reversed by the House.
The House decided to send the impeachment question to the Senate three weeks ago with two-thirds majority.
The Senate leadership said Monday evening it would ignore Maranhao's action.
Senate President Renan Calheiros said the full Senate would move ahead with a planned vote Wednesday on whether Rousseff should be subjected to a trial in the upper chamber on allegations that she illicitly hid a surge in Brazil's budget deficit during her 2014 re-election campaign.
The Senate will decide if Rousseff should be suspended from office for a maximum of 180 days during a detailed legal examination of the charges against her. Vice President Michel Temer would assume presidential duties during her suspension, including opening the Olympics in August.
Rousseff and her supporters have called the impeachment vote an attempted coup and have pointed out she has not been charged with any crime.
Rousseff's presidency has been battered by a recession brought on by a drop in commodities markets and slowing global economy. Unemployment in Brazil rose to 9.6 million workers in 2015.
The stock exchange in Sao Paulo reacted to the news with a 3.5 per cent decline in the Bovespa index, but it recovered to a loss of 1.95 per cent compared with the close of trading on Friday. The exchange rate of the real also fell against the US dollar by 4.75 per cent.