BRASILIA (AFP) - Suspended Brazil President Dilma Roussef denied on Monday (Aug 29) that she had committed an impeachable crime, as she defended herself before senators preparing to vote on removing her from office.

"I did not commit the crimes that I am unjustly accused of," the 68-year-old leftist leader said in an address to the Senate, urging it to vote against impeaching her. "Vote against impeachment, vote for democracy... Do not accept a coup."

Her appearance in front of Brazil's Senate, testifying for the first time at her trial hours before senators were to start voting on her fate, was a dramatic finale to an impeachment trial likely ending 13 years of leftist rule in Latin America's biggest country.

Branding accusations against her "a pretext for a constitutional coup", Ms Rousseff called herself a fighter for democracy.

"I've come to look your excellencies in the eye and to say that I did not commit a crime," she said said in a calm, firm voice from the Senate chamber podium. "I did not commit the crimes for which I have been accused unjustly and arbitrarily."

Ms Rousseff is accused of having taken illegal state loans to patch budget holes. Momentum to push her out is also fueled by deep anger at Brazil's historic recession, political paralysis and a vast corruption scandal centered on state oil giant Petrobras.

The packed Senate chamber crackled with tension as Ms Rousseff came to the showdown accompanied by heavyweight allies, including her presidential predecessor Luiz Inacio Lula da Silva, and a dozen former Cabinet members.

Ms Rousseff, 68, was greeted by cheering supporters as she arrived in the Senate. "Dilma, warrior of the Brazilian homeland!" the crowd of supporters shouted.

A small crowd of loyalists gathered from early morning outside the Senate and supporters shouted "Dilma come back!" from cars as they drove past the building's entrance.

However, there appeared to be little Ms Rousseff could say to save her presidency.

Closing arguments will begin after her testimony on Monday, followed by voting, possibly extending into Wednesday. Opponents say they will easily reach the needed two-thirds majority - 54 of 81 senators - to remove her from office.

In that case, Ms Rousseff's former vice-president turned political enemy, Mr Michel Temer, will be confirmed as president until elections in 2018.

Mr Temer, from the center-right PMDB party, has already been acting president since May, using his brief period in power to steer the government rightward.

He plans to leave Tuesday or Wednesday on his first official foreign trip, a G20 summit in China, where officials say he will push to restore the tattered reputation of Brazil's economy.

Criticised for lacking a popular touch or appetite for backroom politicking, Ms Rousseff has barely double-digit approval ratings.

However, supporters outside the Senate said they backed Ms Rousseff's claim to be victim of trumped up charges in a rightwing coup.

"I am fighting to defend democracy and the dignity of the people. This has been a persecution against the Workers' Party, Dilma and the Brazilian people," said one of about 100 protesters outside the Senate, retired teacher Marlene Bastos, 65.

Although most Brazilians have abandoned Ms Rousseff, there is lingering sympathy for a woman who was imprisoned and tortured by the military dictatorship in the 1970s for belonging to a far left urban guerrilla cell.

Although her presidency has been mired in the Petrobras embezzlement and bribery scandal, Ms Rousseff herself has never been charged with trying to enrich herself - unlike many of her prominent accusers and close allies.

Mr Temer is hardly more popular, according to opinion polls. He faces harsh questioning over his legitimacy as an unelected president and was loudly booed at the recent Olympic opening ceremony in Rio de Janeiro.

The impeachment case rests on narrow charges that Ms Rousseff took unauthorised state loans to bridge budget shortfalls during her 2014 election to a second term.

Allies have spent the Senate trial arguing that these loans were nothing more than stop-gap measures frequently employed by previous governments.

Opponents, however, have broadened the accusation to paint Rousseff's loans as part of her disastrous mismanagement, contributing to once booming Brazil's slide into recession.

Brazil's economy shrank 3.8 per cent in 2015 and is forecast to drop a further 3.3 per cent this year, the worst performance since the 1930s. Inflation stands at around 9 per cent and unemployment at 11 percent.

Ms Rousseff's side says that decline was caused by forces far beyond the President's control, notably a worldwide slump in commodity prices, which hit exports hard.