Dilma Rousseff says there is no justification for removing her as president of Brazil and called her impeachment trial a “coup”.
If found guilty the suspended leader will be formally removed from office, ending 13 years of leftist rule in Latin America’s biggest country.
The 68-year-old was greeted by cheering supporters as she arrived in the Senate to testify for the first time in her defence, hours before senators were to start voting on her fate.
She was accompanied by heavyweight allies including her presidential predecessor Luiz Inacio Lula da Silva and a dozen former cabinet members.
She is accused of having taken illegal state loans to patch budget holes.
She took to the stand for around half an hour, before facing questioning from allies and opponents.
Ms Rousseff said she refused to resign because she is committed to democracy and the rule of law.
She called the accusations against her “a pretext for a constitutional coup”, adding: “I’ve come to look your excellencies in the eye and to say that I did not commit a crime.
“I did not commit the crimes for which I have been accused unjustly and arbitrarily.
“I cannot help but taste the bitterness of injustice. But like I did in the past, I resist. Don’t expect me to stay silent like a coward.”
The voting could last until Wednesday. If they vote to impeach her, Ms Rousseff’s former vice president turned political enemy, Michel Temer, will be confirmed as president until elections in 2018.