A Senate commission sits today to hear Rousseff's defense arguments before submitting its report to Senators at a full impeachment trial scheduled in August.
"My defense tomorrow will be submitted in writing and read out by my lawyer," Rousseff wrote on Twitter.
"We are considering whether I will attend a plenary session of the Senate at another time."
Rousseff was suspended from office in May after lawmakers voted to hold an impeachment trial over allegations that she fiddled government accounts.
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At that point Rousseff will again have the opportunity to appear in person to defend herself.
Brazil hosts the Olympic Games in Rio de Janeiro from August 5 to 21.
If two thirds of the Senate vote to impeach Rousseff, she will be immediately removed from office.
Her former vice-president Michel Temer has replaced her as acting head of state. Several of his ministers have already stepped down over separate corruption allegations.
Brazil is suffering a deep recession and numerous politicians are implicated in a corruption probe centering on state oil firm Petrobras.