Brazilian lawmakers begin to debate over whether to impeach President Dilma Rousseff

Brazilian lawmakers battled through a noisy impeachment debate that could topple President Dilma Rousseff, in a political crisis threatening to destabilize the country months before it hosts the Olympics.

The sessions will lead to a vote on Sunday that could take the 68-year-old leftist leader closer to being driven from office as Latin America's biggest economy struggles through a recession.

The government's lawyer, Jose Eduardo Cardozo, drew noisy complaints in the chamber when he repeated Rousseff's claim that the impeachment drive was a "coup."

Brazil faces a tense weekend as the debates continue and protesters plan to take to the streets.

Rousseff's supporters have been gathering for days in a stadium in the capital Brasilia, where she was expected to visit them on Saturday.

Pro- and anti-Rousseff rallies are also planned in other cities on Sunday, including the economic capital Sao Paulo and Rio de Janeiro, where the Olympics will run from August 5-21.

Police tightly guarded the area around Congress, which was surrounded with metal barriers.

"This is a historic process, there's no doubt," said House Speaker Eduardo Cunha, one of the leaders of the push to remove Rousseff.

Late Thursday, the Supreme Court rejected Rousseff's last-minute bid to have the impeachment proceedings suspended.

She also pulled out of a planned television appearance on Friday after opponents threatened to appeal against it in court.

If the lower house votes to push on with impeachment, Rousseff will be sent to trial in the Senate in a process expected to last months.

- Fending off a 'coup' -

Rousseff is accused of illegally manipulating government accounts.

The accusations and a deep recession have dragged down her popularity.

Latest counts of voting intentions in the lower house by Brazilian newspapers suggest the pro-impeachment camp have the two-thirds majority needed to pass the impeachment motion up to the Senate.

Rousseff vowed to "fight until the last minute... to foil this coup attempt."

She appealed unsuccessfully to the Supreme Court, alleging that the case against her was a vendetta marred by irregularities.

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

She has promised to compromise with opponents if she is allowed to stay in office.

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

"We have come to a decisive phase in this process and the best thing for the country is to have a result on Sunday, whatever it might be," said Leonardo Piciani, PMDB congressional leader.

"We have to turn the page and not waste more time in political battles and disputes," he told AFP.

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 be ousted and Temer would remain in the presidency.

Opposition lawmaker Paulinho da Forca told reporters Friday she had already been discussing "the future government" with "president" Temer.

Cardozo said the government was considering further judicial appeals.

- Lobbying against impeachment -

Rousseff's top ally and predecessor as president, Luiz Inacio Lula da Silva, rallied support for her in a video message.

"We are going to defeat impeachment and end this crisis once and for all," he said.

Lula himself faces corruption allegations linked to a graft scandal at state oil company Petrobras. Cunha also faces corruption charges.

Financial markets have been betting against Rousseff. The Sao Paulo stock exchange rose 5.8 percent this week in anticipation of a vote against her on Sunday, analysts said.