RIO DE JANEIRO (Reuters) - JBS SA, the world's largest beef producer, denied a Saturday newspaper report that it had made illegal payments for President Dilma Rousseff's 2014 reelection campaign.

The O Globo newspaper, citing leaked testimony given to federal investigators by Monica Moura, the wife of Rousseff's campaign chief Joao Santana, earlier reported that JBS paid the Rousseff campaign's debt to Focal, a Sao Paulo-based visual communications firm.

The report did not say how much money JBS allegedly paid to Focal, but said the payment was not declared to electoral authorities.

Moura's accusations come as part of a massive probe into graft at state-run oil company Petrobras, which has ensnared dozens of politicians and CEOs of top construction firms who prosecutors say paid billions in bribes for bloated contracts.

JBS said in an emailed statement it had already "audited all its archives from 2012 to the present" and found no payment to or receipt from Focal.

The company said all its campaign donations were legal and declared to electoral authorities.

Rousseff's office did not return calls and emails seeking comment. At Focal's Sao Paulo office, the phone rang unanswered and an email request for comment bounced back.

The beleaguered Rousseff is expected to be suspended from office within days, as the Senate is expected to vote to continue impeachment proceedings against her related to separate accusations of illegal budgetary maneuvering.

Under Brazil's constitution, Rousseff must be suspended for up to six months while the Senate holds a trial on the matter.

(Editing by Toby Chopra and James Dalgleish)