SAO PAULO -- Brazilian senators on Saturday questioned the last two witnesses summoned by the defence for President Dilma Rousseff in her impeachment trial for allegedly breaking fiscal rules in the management of the federal budget.

In the third day of deliberations, senators questioned former Finance Minister Nelson Henrique Barbosa and Rio de Janeiro State University law professor Ricardo Lodi.

Several days of debate, including an address by Rousseff on Monday, will culminate in a vote on whether to permanently remove her from office.

The Senate voted in May to impeach and suspend her for up to 180 days while the trial could be prepared.

Vice-President Michel Temer took over in May. If Rousseff is removed, Temer will serve the rest of her term through 2018.

She and her supporters say the attempts to remove her from office amount to a coup d'etat.

Rousseff is accused of illegally shifting funds between government budgets. Opposition parties say that was to boost public spending and shore up support while masking the depths of deficits. They claim that her manoeuvrs exacerbated a severe recession in Latin America's largest economy.

Rousseff and her supporters claim that corrupt lawmakers want to oust her so they can water down an investigation into billions of dollars in kickbacks at state oil company Petrobras.

The two-year investigation has led to the jailing of dozens of businessmen and politicians, and threatens to bring down many more.

On Friday, Rousseff's defence called experts to testify and answer questions, a day after the prosecution dominated Thursday's session.

Luiz Gonzaga Belluzzo, an economist, argued that Rousseff had not broken so-called fiscal responsibility laws. He said that instead of hiding government spending, as critics argue, in early 2015 she was coming up with contingency plans to maintain spending in the face of declining revenues.