Rival protests have taken place in Brazil's capital in the run-up to a crucial Congress vote on Sunday that will decide whether President Dilma Rousseff will face an impeachment trial at the Senate.

Tens of thousands of pro-government supporters, largely union members and land reform activists, came by bus to Brasilia from across the country to defend Rousseff and her left-leaning Workers' Party.

They credit the party for unprecedented improvements in their lives.

Al Jazeera's Gabriel Elizondo, reporting from Brasilia, said the pro-Rousseff supporters were "trying to pressure lawmakers" against voting for her impeachment.

He added that former President Luiz Inacio Lula da Silva gave a speech at the rally offering his support to the embattled Rousseff.

"His key message to these people was 'stick with the president, stick with Dilma Rousseff'. He is telling them that they are going to defeat this impeachment process against Rousseff," our correspondent said.

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Just a boulevard away, several hundred anti-government protesters rallied demanding Rousseff's removal.

They blamed her for the tanking economy and the plague of corruption, which are reflected in the country's sky-high taxes and dismal public hospitals, schools and other basic services.

The two rival camps of demonstrators in Brazil's capital underscore the sharp ideological divide that is playing out in Congress as politicians debate whether to oust the president.

The Supreme Court, in a majority ruling, rejected Rousseff's attempt to have the impeachment move suspended [EPA]

Both sides had previously pledged to flood the city with supporters before the crucial vote on Sunday in the Chamber of Deputies, which will determine whether the impeachment proceeds to the Senate.

Proponents of impeachment need 342 of 513 votes, and tallies in the main Brazilian news outlets show them hovering near that number.

Rousseff is fighting to survive a political storm prompted by Brazil's worst recession since the Great Depression in the 1930s and a corruption scandal that has reached her inner circle.

She is accused of manipulating budget accounts during re-election in 2014.

"Impeaching a president who has not committed a crime of responsibility is to rip the Brazilian constitution to shreds," Rousseff said in a signed article published Saturday in the Folha de S Paulo newspaper.

"To oppose and criticise my government is part of democracy" she wrote. "But overthrowing a legitimately elected president who committed no crime is not part of democracy. It is a coup."

Rousseff accused her vice president, Michel Temer, and the house speaker of "treachery" and coup-plotting.

She also pledged to "fight until the last minute ... to foil this coup attempt".

But the collapse of her coalition has been relentless, starting with the defection of Temer's PMDB party.

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Temer will take over as interim president if the trial starts in the Senate. Rousseff would have to step down for six months during the proceedings.

If the Senate then voted by a two-thirds majority to impeach her, she would have to resign and Temer would remain in the presidency.

"Both the vice president and the president of the lower house who will guide the impeachment vote have been embroiled in corruption scandals," Mark Langevin, an adjunct professor at George Washington University, told Al Jazeera.

He said what is going on in Brazil is that deputies and power-brokers are debating whether impeachment or the status quo is more divisive for the politically polarised country.

Source: Al Jazeera and agencies