Brazilian President Dilma Rousseff has said impeachment proceedings launched against her in Congress amount to a coup attempt.
In a speech to pro-government lawyers, Ms Rousseff said Brazilian democracy was under attack.
"I have committed no irregularity. I will never resign," she said.
Opposition lawmakers are seeking to remove her over allegations that she manipulated government accounts to hide a growing deficit.
Ms Rousseff, a former political prisoner during Brazil's military government, began her second term in office 14 months ago.
But her popularity has plummeted amid corruption allegations around senior members of the governing Workers' Party.
The speaker of the lower house of Congress, Eduardo Cunha, agreed in December to open impeachment proceedings against her.
"There is just one name for that - a coup," said Ms Rousseff.
"I want tolerance, dialogue and peace. And that will only be possible if democracy is preserved," she said.
Brazilian democracy was restored in 1985, 21 years after the military coup that deposed the left-wing government of Joao Goulart.
The Workers' Party has been in power since Luiz Inacio Lula da Silva was sworn in for his first term in 2003.
Government supporters say the opposition did not accept the results of the 2014 election, in which Ms Rousseff was re-elected for another four-year term, and are trying to remove her by undemocratic means.
Lula's legal battle
Last week, Ms Rousseff suffered another blow when a move to appoint Lula as her chief of staff was blocked by a federal judge.
The government appealed against the decision, but it was later confirmed by a Supreme Court judge. The court is expected to issue a final ruling by the end of the month.
Ms Rousseff had been accused by opposition figures of appointing Lula to shield him from charges of money-laundering which he denies.
The leftist former leader is being investigated for alleged involvement in major corruption at state-owned oil company Petrobras.
Under Brazilian law, cabinet members can be investigated only by the Supreme Court.
During a pro-government demonstration on Saturday, Lula said he was joining the government to help the country and said Brazil, which is in its worst recession in decades, needed to resume growth.
"There will not be a coup against Ms Rousseff," he told cheering supporters.
"Democracy is the only way to allow people to participate in government's decisions," added the former leader.
Lula says he will run for president again in 2018.