BRASILIA, March 3 (Reuters) - Brazilian ruling party Senator Delcido do Amaral, arrested in November on obstruction of justice charges, has agreed to a plea bargain implicating President Dilma Rousseff and ex-President Luiz Inacio Lula da Silva in the Petrobras graft scandal, local media reported on Thursday.
The online version of Brazilian paper O Estado de S.Paulo said Amaral, who was released from jail in February with some restrictions, had given preliminary testimony to public prosecutors outlining what he could reveal if granted leniency in a formal plea bargain.
O Estado did not identify sources for its information but said Amaral had named Lula and said he could outline shady dealings with the purchase of the Pasadena refinery in Texas by Petrobras.
The state-run oil company, formally known as Petroleo Brasileiro SA, has been the center of a nearly two-year corruption scandal that prosecutors are investigating.
Amaral's lawyer had previously said that his client would not give a plea bargain. Attempts to reach his offices for comment on Thursday were unsuccessful.
The public prosecutor's office declined to comment.
Weekly magazine IstoE also said on Thursday that the senator testified in his plea bargain that Rousseff had used her influence to keep directors suspected of corruption in positions at Petrobras.
The presidential palace said it had no comment.
Rousseff had also tried on three occasions to use the Justice Ministry to release suspects in the graft investigation from prison, a clear abuse of powers, IstoE said Amaral testified.
Brazil's Justice Minister Jose Eduardo Cardozo resigned in late February, complaining that he had come under undue pressure from the ruling Workers' Party to interfere in the corruption scandal and investigations into Lula.
IstoE said Amaral had accused Rousseff of appointing a favorable Supreme Court justice to help avert conviction of some directors and statesmen under investigation for bribes and kickbacks at Petrobras.
Amaral also said Lula had full knowledge of a massive graft scheme in Petrobras and tried to block prosecutors from investigating it, according to IstoE, which said it had access to his testimony.
Lula's foundation said they would not comment on the press reports. "We do not know if this plea bargain even exists," Lula Institute spokesman José Chrispiniano said. "(IstoE) has exaggerated in the past."
Federal prosecutors presented formal charges against Amaral on Dec. 7, along with billionaire financier Andre Esteves, accusing them of obstructing a criminal investigation into Petrobras. (Reporting by Anthony Boadle and Reese Ewing in Sao Paulo; Editing by Daniel Flynn and Lisa Von Ahn)